U.S. patent application number 13/812284 was filed with the patent office on 2013-08-15 for pvd-metallic effect pigments with diffractive structure and metal nanoparticles, process for preparing them and use thereof.
This patent application is currently assigned to ECKART GMBH. The applicant listed for this patent is Martin Fischer, Bernhard Geissler, Klaus Greiwe, Frank Henglein, Wolfgang Herzing, Ralph Schneider. Invention is credited to Martin Fischer, Bernhard Geissler, Klaus Greiwe, Frank Henglein, Wolfgang Herzing, Ralph Schneider.
Application Number | 20130209790 13/812284 |
Document ID | / |
Family ID | 44510926 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130209790 |
Kind Code |
A1 |
Geissler; Bernhard ; et
al. |
August 15, 2013 |
PVD-Metallic Effect Pigments with Diffractive Structure and Metal
Nanoparticles, Process for Preparing Them and Use Thereof
Abstract
The invention relates to metallic effect pigment, the metallic
effect pigment having at least one diffractive structure and at
least one layer which comprises metal nanoparticles and metal oxide
phase, the metal of the metal oxide phase and the metal of the
metal nanoparticles in this at least one layer being identical. The
invention further relates to a process for preparing these metallic
effect pigments, to a coating composition, and to a coated
article.
Inventors: |
Geissler; Bernhard;
(Schwarzenbruck, DE) ; Fischer; Martin;
(Koenigstein, DE) ; Henglein; Frank; (Nuernberg,
DE) ; Schneider; Ralph; (Lauf, DE) ; Herzing;
Wolfgang; (Neunkirchen, DE) ; Greiwe; Klaus;
(Lauf, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Geissler; Bernhard
Fischer; Martin
Henglein; Frank
Schneider; Ralph
Herzing; Wolfgang
Greiwe; Klaus |
Schwarzenbruck
Koenigstein
Nuernberg
Lauf
Neunkirchen
Lauf |
|
DE
DE
DE
DE
DE
DE |
|
|
Assignee: |
ECKART GMBH
Hartenstein
DE
|
Family ID: |
44510926 |
Appl. No.: |
13/812284 |
Filed: |
July 21, 2011 |
PCT Filed: |
July 21, 2011 |
PCT NO: |
PCT/EP11/62544 |
371 Date: |
April 2, 2013 |
Current U.S.
Class: |
428/329 ;
106/403; 106/404; 428/328; 428/330 |
Current CPC
Class: |
C09C 2200/1004 20130101;
C09C 2200/30 20130101; C01P 2004/64 20130101; C09D 5/36 20130101;
C09D 7/68 20180101; C01P 2004/04 20130101; Y10T 428/258 20150115;
Y10T 428/256 20150115; C01P 2004/03 20130101; C01P 2002/85
20130101; C01P 2006/65 20130101; C09D 7/67 20180101; C09C 2210/30
20130101; C09C 2210/40 20130101; C09C 1/0015 20130101; C09D 7/62
20180101; C09C 2220/20 20130101; C01P 2006/66 20130101; C09C 1/62
20130101; C09C 2200/502 20130101; C09C 2200/405 20130101; B82Y
30/00 20130101; C01P 2006/62 20130101; C09C 1/0018 20130101; C09C
2200/407 20130101; Y10T 428/257 20150115 |
Class at
Publication: |
428/329 ;
106/403; 106/404; 428/328; 428/330 |
International
Class: |
C09C 1/62 20060101
C09C001/62 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 27, 2010 |
DE |
10 2010 032 399.3 |
Claims
1. A metallic effect pigment comprising at least one diffractive
structure and at least one layer which comprises metal
nanoparticles and metal oxide phase, the metal of the metal oxide
phase and the metal of the metal nanoparticles being identical in
this at least one layer.
2. The metallic effect pigment of claim 1, wherein the at least one
layer which comprises metal nanoparticles and metal oxide phase
comprises the at least one diffractive structure.
3. The metallic effect pigment of claim 1, wherein the metal of the
at least one layer which comprises metal nanoparticles and metal
oxide phase is selected from the group consisting of aluminum,
magnesium, chromium, silver, copper, gold, zinc, tin, manganese,
iron, cobalt, nickel, titanium, tantalum, molybdenum, tungsten,
mixtures thereof; and alloys thereof.
4. The metallic effect pigment of claim 1, wherein the average size
of the metal nanoparticles is in a range from 1 to 50 nm.
5. The metallic effect pigment of claim 1, wherein in the at least
one layer which comprises metal nanoparticles and metal oxide
phase, the average content of metal M and oxygen is at least 80
atom %, based on this one layer.
6. The metallic effect pigment of claim 1, wherein the at least one
diffractive structure has at least one periodic pattern with
diffractive elements.
7. The metallic effect pigment of claim 6, wherein the periodic
pattern has 5000 to 20,000 diffractive elements/cm.
8. The metallic effect pigment of claim 1, wherein the diffractive
structure has a depth of at least 40 nm.
9. The metallic effect pigment of claim 1, wherein an average layer
thickness of the at least one layer which comprises metal
nanoparticles and metal oxide phase is in a range from 8 to 500
nm.
10. The metallic effect pigment of claim 1, wherein the at least
one layer which comprises metal nanoparticles and metal oxide phase
has a first outer face and a second outer face, the amount of metal
nanoparticles in the first outer face and in the second outer face
of this layer being different from one another and differing by at
least 10 atom %.
11. The metallic effect pigment of claim 1, wherein the metallic
effect pigment has two layers disposed one atop the other, with at
least one layer comprising metal nanoparticles in a metal oxide
phase, and this at least one layer has a first outer face and a
second outer face, the amount of metal nanoparticles in the first
outer face and in the second outer face of this at least one layer
being different from one another and differing by at least 10 atom
%.
12. The metallic effect pigment of claim 1, wherein the metallic
effect pigment has three or more layers disposed atop one another,
with at least one layer comprising metal nanoparticles in a metal
oxide phase; the at least one layer has a first and a second outer
face, the metallic effect pigment has a first outer face and a
second outer face, and the highest amount of metal nanoparticles is
present in the first or in the second outer face of the metallic
effect pigment, and the amount of metal nanoparticles in the first
and in the second outer face of this at least one layer differs by
at least 10 atom %.
13. The metallic effect pigment of claim 1, wherein the amount of
metal nanoparticles changes continuously over the thickness of the
at least one layer which comprises metal nanoparticles and metal
oxide phase.
14. The metallic effect pigment of claim 13, wherein the amount of
metal nanoparticles changes at least partly with a gradient of 0.1
to 4 atom %/nm over the thickness of the at least one layer which
comprises metal nanoparticles and metal oxide phase.
15. The metallic effect pigment of claim 1, wherein the amount of
metal nanoparticles changes discontinuously between two successive
layers.
16. The metallic effect pigment of claim 1, wherein the metal is a
trivalent metal and the metallic effect pigment has at least one
first and one second successive layer, the first layer comprising
metal nanoparticles and the second layer comprising elemental
metal, the amount of metal nanoparticles in the outer face of the
first layer, which comprises metal nanoparticles and metal oxide
phase, being in a range from 1 to 50 atom %, and the amount of
elemental metal in the outer face of the second layer being in a
range from 60 to 95 atom %, with the proviso that the difference in
the amount of metal nanoparticles and of elemental metal in the two
outer faces is at least 10 atom %.
17. The metallic effect pigment of claim 1, wherein the metal is a
tetravalent metal and the metallic effect pigment has at least one
first and one second successive layer, the first layer comprising
metal nanoparticles and the second layer comprising elemental
metal, the amount of metal nanoparticles in the outer face of the
first layer, which comprises metal nanoparticles and metal oxide
phase, being in a range from 1 to 50 atom %, and the amount of
elemental metal in the outer face of the second layer being in a
range from 60 to 95 atom %, with the proviso that the difference in
the amount of metal nanoparticles and of elemental metal in the two
outer faces is at least 10 atom %.
18. The metallic effect pigment of claim 1, wherein the amount of
metal nanoparticles is largely homogeneous over the thickness of
the at least one layer which comprises metal nanoparticles and
metal oxide phase.
19. The metallic effect pigment of claim 1, wherein the at least
one layer which comprises metal nanoparticles and metal oxide phase
has an average oxygen content of 30 to 77 atom %, based on the
total amount of metal and oxygen in this layer.
20. The metallic effect pigment of claim 1, wherein the metallic
effect pigment comprises at least three layers: A) a layer A which
has at least one metal M.sub.A and an average oxygen content
O.sub.A, based on the total amount of M.sub.A and O.sub.A in the
layer A, B) a layer B with at least one metal M.sub.B and an
average oxygen content O.sub.B of 0 to 77 atom %, based on the
total amount of M.sub.B and O.sub.B in the layer B, and C) a layer
C which has at least one metal M.sub.C and an average oxygen
content O.sub.C, based on the total amount of M.sub.C and O.sub.C
in the layer C, the average oxygen content O.sub.AC in the layers A
and C being determined in accordance with the formula (I) O AC = 1
2 ( O A M A + O A + O C M C + O C ) ( I ) ##EQU00002## and being in
a range from 8 to 77 atom %, with the proviso that at least one of
the layers, A, B, or C, comprises metal nanoparticles.
21. The metallic effect pigment of claim 1, wherein the metallic
effect pigment is enveloped with an anticorrosion layer which is
optionally surface-modified.
22. A coating composition comprising the metallic effect pigment of
claim 1.
23. An article provided with the metallic effect pigment of claim
1.
24. A process for preparing a metallic effect pigment comprising:
(a1) applying a release layer to a linearly movable substrate, (a2)
introducing a diffractive structure into the release layer,
preferably by embossing, and (a3) applying at least one metal to
the release layer on the linearly movable substrate, in a vacuum
chamber having a vapor-deposition section, by means of reactive
physical vapor deposition (PVD), in the presence of oxygen, or (b1)
applying a release layer to a linearly movable substrate, (b2)
applying at least one metal to the release layer on the linearly
movable substrate, in a vacuum chamber having a vapor-deposition
section, by means of reactive physical vapor deposition (PVD), in
the presence of oxygen, and (b3) introducing a diffractive
structure onto and/or into at least one surface of the PVD layer
applied in step (b2), preferably by embossing, and also c)
detaching the applied PVD layer(s) provided with a diffractive
structure, d) comminuting the detached PVD layer(s), e) optionally
transferring the comminuted PVD layer(s) into a dispersion or
paste.
25. The metallic effect pigment of claim 6, wherein the at least
one diffractive structure has at least one periodic pattern with
diffractive elements comprising geometric shapes or bodies.
26. The metallic effect pigment of claim 1, wherein the diffractive
structure is selected from the group consisting of symmetrical
triangles, asymmetrical triangles, grooves, rectangles, circles,
wavy lines, cones, truncated cones, knobs, prisms, pyramids,
truncated pyramids, cylinders, hemispheres, and combinations
thereof.
27. The metallic effect pigment of claim 1, wherein the metallic
effect pigment further comprises smooth sections present on the
metallic effect pigment surface.
28. The metallic effect pigment of claim 10, wherein at least one
outer face has a depth of approximately 10 nm.
29. The metallic effect pigment of claim 1, wherein the layer
further comprises extraneous elements selected from the group
consisting of one or more of nitrogen, sulfur, carbon,
hydrogen.
30. The metallic effect pigment of claim 21, wherein the
anticorrosion layer comprises a protective material selected from
the group consisting of metal oxide, plastic, and combinations
thereof.
31. The metallic effect pigment of claim 30, wherein the metal
oxide is selected from the group consisting of silicon oxide,
aluminum oxide, cerium oxide and mixtures thereof.
32. The metallic effect pigment of claim 30, wherein the plastic is
selected from the group consisting of polyacrylate,
polymethacrylate, and mixtures thereof.
33. The metallic effect pigment of claim 30, wherein the metal
oxide layer comprises one or more reactive functional organic
groups selected from the group consisting of acrylic, methacrylic,
vinyl, epoxy, hydroxyl, amino, and mercapto groups.
34. A coated article coated with a coating composition comprising
the metallic effect pigment of claim 1.
Description
[0001] The invention relates to a dark metallic effect pigment
which has diffractive structures, to a process for preparing these
pigments, and to their use.
[0002] Metallic effect pigments have been used for many years in
coatings in order to generate a metallic effect.
[0003] Conventional metallic effect pigments consist of
platelet-shaped metallic pigments whose effect derives from the
directed reflection of incident light at the metallic pigments of
lamellar form which are oriented in parallel in the respective
application medium.
[0004] Typical fields of application of the metallic effect
pigments are the coatings industry, especially the automotive
industry, the printing industry, and the plastics industry.
[0005] Metallic effect pigments produced by PVD techniques have
been known for some considerable time. They are notable for
extremely high luster, immense covering power, and unique optical
properties. Owing to their low thickness of around 30 to 70 nm and
their extremely smooth surfaces, they have a tendency, following
application, to conform very closely to the substrate. If the
substrate is very smooth, the result is virtually a mirrorlike
appearance.
[0006] Likewise known are metallic effect pigments, produced by PVD
techniques, that have a regular embossed structure. This structure
is able to act as an optical lattice, and breaks incident light
down into its spectral colors. As a consequence of this, these
pigments generate a colorfully shimmering color effect ("rainbow
effect") in unison with the typical properties of metallic pigments
such as high luster, high brightness, and very good hiding power.
Pigments of this kind are disclosed for example in U.S. Pat. No.
5,624,076 and also in U.S. Pat. No. 6,692,830 B2.
[0007] Cosmetic applications of such pigments are disclosed in EP 1
694 288 B1. They are in commerce under the trade names
Holographic.RTM. or Metalure Prismatic.RTM..
[0008] The company Flex (Santa Rosa, Calif., USA) offers pigments
under the trade name Spectraflair.RTM.. The structure and
production of these pigments are described in Barbara Parker
"Advances in Interference Color", in the conference volume of the
Color Cosmetic Summit, Montreal (2003). These pigments are
multilayer metallic effect pigments generated by PVD techniques,
having a central core of aluminum with layers of MgF.sub.2 applied
to it. Embossed onto these layers of low refractive index is a
lattice with a defined spacing of the lattice structures. These
pigments generate extremely strong rainbow effects.
[0009] In order to generate a dark metallic effect and at the same
time a rainbow effect, the known metallic effect pigments with
rainbow effect can be tinted with commercially available black
pigments. A disadvantage, however, is that such formulations always
have a disadvantageous brown tinge. This occurs particularly at
shallow angles of observation and/or incidence.
[0010] EP 1 522 606 A1 describes the production of a film
comprising black aluminum oxide. Neither metallic effect pigments
nor multilayer structures are disclosed therein. The films that are
disclosed therein have no significant metallic effect with luster
and flop.
[0011] U.S. Pat. No. 4,430,366 describes the production of films
which comprise a sequence of inherently homogeneous layers of metal
and metal oxide. Here, again, there is no mention of metallic
effect pigments.
[0012] DE 69601432 T2 relates to a method for thermal generation of
an image on a substrate, where an oxygen-containing, black aluminum
layer is applied in such a way that the layer has an optical
transmission of at least 0.3 at a wavelength between 200 and 1100
nm. This document, again, does not relate to the provision of
metallic effect pigments.
[0013] EP 1 144 711 B1 discloses a method for producing reflective
color pigments, in which, to a reflection layer, at least one layer
which brings about a color change and comprises a transparent
material having a refractive index of greater than 1.8, typically
metal oxide, and a light-absorbing metal is applied with
simultaneous evaporation, the light-absorbing metal being different
to the metal of the metal oxide. In terms of process engineering,
the method is very hard to control.
[0014] DE 10 2007 007 908 A1 discloses dark metallic effect
pigments which are produced by PVD techniques. They have a largely
homogeneous composition and possess a relatively high oxygen
content of 25 to 58 atom %. The layer is dark because the metal is
in the form of small metal nanoparticles in dispersion in metal
oxide. Metal effect pigments of this kind produce dark and yet
highly lustrous metallic effect pigments with a pronounced
light/dark flop. The pigments, however, do not exhibit any rainbow
effect.
[0015] WO 2009/012995 A1 discloses three-layer metallic effect
pigments which are likewise able to produce very dark metallic
effect pigments. Here again, however, there is no rainbow
effect.
[0016] It is an object of the present invention to provide a dark
and/or colored metallic effect pigment featuring metallic luster
and a rainbow effect. In applications pigmented with these
pigments, they are not to exhibit any brown tinge, particularly at
shallow angles of incidence and/or observation. With particular
advantage, instead, a blue tinge is to be visible.
[0017] An object of the invention additionally is to prepare highly
lustrous effect pigments with a metallic effect and with different
base shades in conjunction with a rainbow effect.
[0018] An object of the invention in particular is to provide
gold-colored effect pigments with a metallic effect and with a
rainbow effect.
[0019] The effect pigments of the invention are to be able to be
provided by means of simple preparation processes.
[0020] The object on which the invention is based is achieved
through provision of a metallic effect pigment, the metallic effect
pigment having at least one diffractive structure and at least one
layer which comprises metal nanoparticles and metal oxide phase,
the metal of the metal oxide phase and the metal of the metal
nanoparticles being identical in this at least one layer.
[0021] Preferred embodiments are specified in dependent claims 2 to
21.
[0022] The object of the invention is further achieved through
provision of a coating composition which comprises the metallic
effect pigments of any of claims 1 to 21.
[0023] The object is also achieved by provision of a coated article
provided with metal effect pigment of any of claims 1 to 21 or with
a coating composition of the invention.
[0024] According to one preferred variant of the invention, the
coating composition is selected from the group consisting of
coatings, paints, automotive paints, powder coatings, printing
inks, digital-printing inks, plastics, and cosmetic
formulations.
[0025] Lastly, the object of the invention is also achieved through
provision of a process for preparing the metallic effect pigments
of any of claims 1 to 21, the process comprising the following
steps: [0026] (a1) applying a release layer to a linearly movable
substrate, [0027] (a2) introducing a diffractive structure into the
release layer, preferably by embossing, [0028] (a3) applying at
least one metal to the release layer on the linearly movable
substrate, in a vacuum chamber having a vapor-deposition section,
by means of reactive physical vapor deposition (PVD), in the
presence of oxygen, [0029] or [0030] (b1) applying a release layer
to a linearly movable substrate, [0031] (b2) applying at least one
metal to the release layer on the linearly movable substrate, in a
vacuum chamber having a vapor-deposition section, by means of
reactive physical vapor deposition (PVD), in the presence of
oxygen, [0032] (b3) introducing a diffractive structure onto and/or
into at least one surface of the PVD layer applied in step (b2),
preferably by embossing, and also [0033] c) detaching the applied
PVD layer(s) provided with a diffractive structure, [0034] d)
comminuting the detached PVD layer(s), [0035] e) optionally
transferring the comminuted PVD layer(s) into a dispersion or
paste.
[0036] In accordance with the invention, the designation "metallic
effect pigment" also comprehends "metallic effect pigments".
[0037] A "metallic effect pigment" is a laminar metal pigment. The
metallic effect pigment of the invention is a metallic effect
pigment produced by physical vapor deposition (PVD), and may also
be referred to as a PVD metallic effect pigment.
[0038] The metal nanoparticles may also be referred to as metal
clusters.
[0039] In one preferred embodiment of the invention, the metal
nanoparticles are present preferably substantially in a metal oxide
phase or metal oxide matrix, more preferably completely in a metal
oxide phase or metal oxide matrix.
[0040] It has surprisingly been found that metallic effect pigments
having a well-pronounced optical rainbow effect in conjunction with
a very wide variety of base shades can be obtained. For instance,
depending on the size of the metal nanoparticles, in the case of
aluminum nanoparticles, for example, it is possible to set a dark
base shade or a golden base shade. Additionally, via the setting of
the layer thickness of the layer comprising metal nanoparticles in
a metal oxide matrix, it is possible to obtain a base shade which
may be, for example, gold, violet, blue, or black, and/or dark.
[0041] The present invention accordingly enables the provision of
metallic effect pigments having interesting optical properties. A
great advantage is that these metallic effect pigments can be
prepared inexpensively. Thus it is possible, for example, to
produce gold-colored aluminum effect pigments with rainbow effect.
These gold-colored aluminum effect pigments can be used in place of
the substantially more expensive brass effect pigments.
[0042] The metallic effect pigments of the invention are metallic
and produce a metallic effect to a viewer, despite the fact that
the metallic effect pigments comprise metal oxide in a significant
fraction. This result is very surprising and can probably be
attributed to the specific structure of the metallic pigments of
the invention--that is, to the arrangement of metal nanoparticles
in a metal oxide matrix.
[0043] In one preferred embodiment, the at least one layer which
comprise metal nanoparticles and metal oxide phase comprises the at
least one diffractive structure. According to further preferred
embodiments, the diffractive structure is at least partially shaped
into the at least one layer which comprises metal nanoparticles and
metal oxide phase, and/or this at least one layer is shaped to form
a diffractive structure. In one variant of the invention, the
metallic effect pigment has the diffractive structure(s) only on
the top or bottom surface of the metallic effect pigments.
[0044] In one particularly preferred embodiment, the entire layer
is shaped to form a diffractive structure. In this way a
particularly strong "rainbow effect" is achieved.
[0045] The physical principle underlying this rainbow effect is the
diffraction of incident light at the diffractive structure(s).
Accordingly, the coloring of the metallic effect pigments of the
invention differs fundamentally from that of--for example--colored
interference effects. In the case of interference structures, a
wide variety of different shades are obtained as a result of a
suitable sequence of layers of high and low refractive index. There
are countless interference pigments known here in the prior art. In
the case of what are called multilayer layers, a suitable
substrate, such as a platelet-shaped mica, a glass flake, or
metallic effect pigments such as an aluminum effect pigment, is
populated with at least one layer stack of alternating high-index,
low-index, and high-index layers. Effect pigments of this kind may
likewise generate color flops, i.e., different colors at different
angles of incidence and/or of viewing. Nevertheless, the effects
obtained therewith are not comparable with the rainbow effects that
can be achieved with diffractive effect pigments.
[0046] The diffractive structure(s) has or have preferably a
periodic pattern with diffractive elements. The periodic pattern
here refers to the smallest unit of the diffractive elements. The
periodic diffractive structure preferably has 5000 to 20 000
diffractive elements/cm, more preferably 8000-18 000 diffractive
elements/cm, and very preferably 9000-16 000 diffractive
elements/cm. Within this range, primarily visible light (about 400
to 800 nm in wavelength) is diffracted in accordance with the known
principle of a diffraction lattice, with the viewer perceiving a
rainbow effect as a result. It is, however, also possible for
fractions of the IR radiation and/or the UV radiation to be
diffracted.
[0047] The periodicity substantially determines the diffracted
wavelengths of the incident light. Specifically, this may be
calculated in accordance with known formulae, as can be found in
U.S. Pat. No. 6,692,830 B2.
[0048] Diffractive elements contemplated include, for example
symmetrical triangles, asymmetrical triangles, grooves in a wide
variety of different forms, rectangle functions, circles, wavy
lines, cones, truncated cones, knobs, prisms, pyramids, truncated
pyramids, cylinders, hemispheres, etc., and also combinations of
these geometric forms and bodies.
[0049] Geometric bodies having one or more surfaces disposed
parallel to the pigment surface, such as truncated cones, truncated
pyramids, cylinders, or rectangle functions, for example, have a
higher reflection capacity on account of these surfaces.
[0050] Geometric bodies which, relative to the pigment surface,
have inclined side faces intensify the rainbow effect. Inclined
side faces are side faces which, based on the substrate, have an
angle of 5 to 89.degree., preferably of 15 to 84.degree., more
preferably of 27 to 80.degree., more preferably still of 43 to
74.degree.. Examples of suitable geometric bodies include cones,
truncated cones, pyramids, truncated pyramids, etc.
[0051] In the case of truncated pyramids, there is for example a
reflection at the top face parallel to the pigment surface, and an
intensification of the rainbow effect at the cylindrical surface.
Correspondingly, in the case of truncated pyramids, there is
reflection at the top face and an intensification of the rainbow
effect at the inclined side faces.
[0052] In the case of truncated cones or truncated pyramids it is
of course also possible to dispose the top face not parallel to the
pigment surface but instead at an incline relative to the pigment
surface.
[0053] Via the geometric bodies disposed by embossing and/or
shaping on the pigment surface it is possible to intensify the
rainbow effect and/or the reflection capacity of the metallic
effect pigment of the invention, or to change the relative ratio of
rainbow effect to reflection.
[0054] Accordingly, the geometric bodies may be present separated
in sections or else mixed with one another. It is also possible of
course, to dispose the geometric forms and geometric bodies with
superimposition, so that, for example geometric bodies are disposed
additionally on a wavy structure.
[0055] According to one further variant of the invention,
unembossed or unshaped, and therefore smooth, sections may be
present on the metallic effect pigment surface, as well as embossed
and/or shaped sections. By this means as well it is possible to
change the relative ratio of rainbow effect to reflection.
[0056] Preferably the entire surface of the metallic effect pigment
is provided, preferably by embossing, with the diffractive
structure. It is also possible, however, for only part of the
metallic effect pigment surface to be provided, preferably by
embossing, with the diffractive structure, and/or to be shaped to
form a diffractive structure. It is preferred for at least 60%,
more preferably at least 75%, and very preferably at least 90% of
the metallic effect pigment surface to be embossed with a
diffractive structure or shaped to form a diffractive
structure.
[0057] In one particularly preferred embodiment, the diffractive
structure comprises or consists of wavy--for example,
sinusoidal--lines, cones, or truncated cones. In an especially
preferred embodiment, the diffractive structure comprises or
consists of sinusoidal lines, since first this form is particularly
easy to emboss and secondly it produces a very strong diffraction
effect. In the case of these sinusoidal lines, the diffractive
structure is preferably embossed on the whole metallic effect
pigment.
[0058] In order to be able to obtain a distinctly perceptible
effect, the diffractive structure preferably has a certain minimum
depth, since otherwise it is not possible adequately to develop the
physical effect of diffraction. The diffractive structure ought
therefore preferably to have a depth (measured as "peak to valley")
of at least 40 nm, preferably 40 nm to 600 nm, and more preferably
of 50 nm to 400 nm, and very preferably of 100 nm to 250 nm. Above
600 nm, the structure as a whole may no longer have stability.
[0059] It is preferred for the average layer thickness of the at
least one layer which comprises metal nanoparticles and metal oxide
phase to be in a range from 8 to 500 nm. According to a further
preferred embodiment a range from 12 to 200 nm, more preferably
from 15 to 130 nm.
[0060] The depth of the diffractive structure may therefore exceed
the average layer thickness of the at least one layer which
comprises metal nanoparticles and metal oxide phase. This is
preferably the case especially when the entire at least one layer
is shaped to form a diffractive structure.
[0061] According to one preferred development of the invention, the
metal of the at least one layer which comprises metal nanoparticles
and metal oxide phase is selected from the group consisting of
aluminum, magnesium, chromium, silver, copper, gold, zinc, tin,
manganese, iron, cobalt, nickel, titanium, tantalum, molybdenum,
tungsten, mixtures thereof, and alloys thereof. With particular
preference the metal of the at least one layer which comprises
metal nanoparticles and metal oxide phase is selected from the
group consisting of aluminum, chromium, and titanium, mixtures
thereof, and alloys thereof.
[0062] According to one preferred development of the invention, the
average size of the metal nanoparticles is in a range from 1 to 50
nm. Very suitable size ranges have also been found to be average
diameters from a range from 1.5 to 30 nm, more preferably from 2 to
13 nm.
[0063] The base shade of the metallic effect pigments of the
invention is established preferably by the average size of the
metal nanoparticles. Accordingly, the coloring of the metallic
effect pigments differs generally in dependence on the average size
of the metal nanoparticles.
[0064] A small average size of metal nanoparticle refers more
particularly to those particles which are in a size range from 1 to
10 nm, more particularly from 2 up to 8 nm. The average size of the
metal nanoparticles is typically at least 4 nm.
[0065] A large average size of metal nanoparticle refers more
particularly to those particles which are in a size range of more
than 10 nm, more particularly of up to 50 nm. In the case of one
very suitable variant of the invention, the average size of the
large metal nanoparticles is in a range from 15 to 30 nm.
[0066] The coloring and/or the intensity of color may also be
dependent on the thickness of the layer comprising metal
nanoparticles and metal oxide phase.
[0067] The at least one layer comprising metal nanoparticles in a
metal oxide matrix, or two or more layers each of which may
comprise metal nanoparticles in a metal oxide matrix, give a dark
to black visual impression according to layer thickness and size of
the metal nanoparticles.
[0068] It is thought that the metal nanoparticles present in or
embedded in the oxide matrix are in electronic interaction. The
metal nanoparticles exhibit extremely strong absorption of
electromagnetic radiation. In contrast to a pure metal ("bulk"
metal), the metal atoms are not connected electronically to one
another to such an extent that the typical metallic reflection
occurs. The overall effect is therefore one of a dark color.
[0069] The size of the metal nanoparticles can be determined by
means of TEM analysis. In this case the sample is preferably
prepared as elucidated later on below, and the micrographs--in
which the metal nanoparticles appear dark on account of their high
scattering cross section for the electrons--are analyzed. For
determination of the average size, at least 70 particles are
counted and the arithmetic mean is formed. The average size of the
metal nanoparticles is preferably in a range from 1 to 50 nm, more
preferably 1.5 to 30 nm, and very preferably 2 to 10 nm.
[0070] For determining the layer thicknesses, the metal, and the
amounts of metal nanoparticle and of metal oxide, it is possible,
generally, to use the methods indicated in the examples, such as
ESCA (chemical analysis with photoelectron spectroscopy).
[0071] The inventors have found that, surprisingly, it is possible
to influence or modify the base color of the metallic effect
pigments by way of the size of the metal nanoparticles present in
the metal oxide phase. For example, in the case of aluminum,
gold-colored aluminum effect pigments are obtained if the aluminum
nanoparticles present in aluminum oxide have an average size in a
size range from 15 to 28 nm, preferably from 18 to 25 nm, more
preferably at about 20 nm.
[0072] Where, in contrast, the aluminum nanoparticles which are
present in the aluminum oxide have an average size which is within
a range from 2 to 13 nm, more preferably from 5 to 12 nm, more
preferably still at about 10 nm, aluminum effect pigments are
obtained which have a dark or black base shade.
[0073] The metallic effect pigments of the invention with dark or
black base shade can also be mixed with further effect pigments, as
for example unembossed metallic effect pigments and/or pearlescent
pigments. In this case a pigment mixture is obtained which
following application of a paint pigmented with this pigment
mixture, or an ink, produces a coating having a hidden rainbow
effect. The rainbow effect is then perceptible substantially only
in direct sunlight or in another strong white light source. A
pigment mixture of this kind or a correspondingly pigmented paint
or an ink are suitable more particularly for use as a security
feature.
[0074] Accordingly, via the adjustment of the average size of the
metal nanoparticles, the present invention, in a surprisingly
simple way, allows the generation of a wide variety of different
base shades, which are perceived together with a rainbow effect and
allow extremely interesting color design.
[0075] The color impression given by the metallic effect pigments
can additionally be modified as well via the set thickness of the
layer in which the metal nanoparticles are present in the metal
oxide phase.
[0076] In accordance with a further preferred embodiment, the
average amount of metal nanoparticles in the at least one layer
comprising metal nanoparticles and metal oxide phase is in a range
from 1 to 50 atom %, more preferably from 3 to 40 atom %, very
preferably from 4 to 35 atom %, and especially preferably from 5 to
20 atom %, based in each case on the total amount of metal and
oxygen in said layer.
[0077] In the case of a layer thickness from a range from 50 to 80
nm, preferably from 55 to 75 nm, and preferably comprising Al
and/or Cr as metal, and with an oxygen content from a range from 55
atom % to 70 atom %, metal nanoparticles are present in finely
divided form. Metallic effect pigments having this composition are
of transparent gold color.
[0078] If the layer thickness is increased further, the resulting
metallic effect pigments are initially red, then violet, and
finally blue and transparent.
[0079] In this way, gold-colored, transparent, prismatic Al
pigments which in particular are free from heavy metal can be
described.
[0080] Transparent prismatic Cr pigments are notable for corrosion
resistance and high color intensity.
[0081] According to one variant of the invention, the amount of
metal nanoparticles over the thickness of the at least one layer
comprising metal nanoparticles and metal oxide phase is largely
homogeneous, preferably homogeneous. By "homogeneous" is meant in
this context that, over the thickness of the layer in which the
metal nanoparticles are present in the metal oxide, there is
largely no gradient in terms of the concentration of the metal
nanoparticles. The metal nanoparticles are therefore distributed
uniformly over the thickness of the layer. The concentrations of
elemental metal that are determined by means of ESCA and sputter
profiles are the criterion here for the presence of a largely
homogeneous concentration of the metal nanoparticles along the at
least one layer.
[0082] According to a further variant of the invention, the at
least one layer which comprises metal nanoparticles and metal oxide
phase has a first outer face and a second outer face, the amount of
metal nanoparticles in the first outer face and in the second outer
face of this layer being different from one another and differing
by at least 10 atom %.
[0083] An outer face for the purposes of the invention means a
depth of approximately 10 nm. This depth corresponds to the usual
signal depth in the ESCA method that can be used to determine the
concentration of the metal oxide and/or of the metal
nanoparticles.
[0084] In accordance with the invention it is therefore possible to
provide asymmetrical metallic effect pigments. If the metal effect
pigments of the invention are in single-layer form, the outer faces
in that layer are also the outer faces of the metallic effect
pigment. The base color of the metallic effect pigments may also
vary in dependence on the concentration of the metal nanoparticles
in the metal oxide phase. Since the orientation of the metallic
effect pigments, in a paint or in a printing ink, for example,
varies statistically in relation to the position of the outer face,
it is therefore possible, with one metallic effect pigment, to
generate mixtures of shades which at the same time exhibit a
rainbow effect. This allows interesting colorations. Moreover,
these asymmetrically constructed pigments can be produced in a more
easily reproducible way.
[0085] It is further preferred for the metallic effect pigment to
have two layers arranged one atop the other, with at least one
layer comprising metal nanoparticles in a metal oxide phase, and
for this at least one layer to have a first outer face and a second
outer face, and for the amount of metal nanoparticles in the first
outer face and in the second outer face of this at least one layer
to be different from one another and to differ by at least 10 atom
%.
[0086] In the case of this variant of the invention, the at least
one layer comprising metal nanoparticles and metal oxide phase or
metal oxide matrix may have been applied to a metallic layer. The
metallic layer in this case preferably has a layer thickness of at
least 2 nm, preferably at least 5 nm. A layer thickness in a range
0.15 from 5 to 30 nm, preferably from 7 to 25 nm, has proven very
suitable. In this layer-thickness range, the metal layer has
strongly absorbing properties, and so the metallic effect pigments
overall produce a darker or more restrained impression of
color.
[0087] The metal layer can of course also have a greater thickness,
as for example in a range from 30 to 250 nm, preferably from 35 to
180 nm. A range from 38 to 74 nm as well has proven very suitable.
In the case of these greater layer thicknesses, the metal layer is
strongly reflecting and lustrous.
[0088] The color impression of these two-layer metallic effect
pigments can be adjusted via the layer thickness and/or the average
size of the metal nanoparticles in the metal oxide phase or metal
oxide matrix. As the layer thickness increases, the perceived color
goes from gold through red and on to blue. These base shades are
possessed by the metallic effect pigments of the invention in
addition to the rainbow effect.
[0089] With a constant ratio of oxygen to metal, for example, and
hence on application of a layer having a constant size of metal
nanoparticles in a metal oxide matrix to a metal layer, the
aforementioned base shades can be produced.
[0090] Thus, for example, chromium effect pigments having a
two-layer structure, comprising an aluminum metal layer and a layer
with chromium nanoparticles embedded in chromium oxide, where the
oxygen fraction, based on the total amount of oxygen and chromium
in this layer, is in a range from 30 to 58 atom %, have the
following base shade depending on the layer thickness:
Example A:
[0091] Aluminum layer thickness: 15 nm [0092] Thickness of the
layer with chromium nanoparticle in chromium oxide: 15 nm [0093]
Base shade: gold
Example B:
[0093] [0094] Aluminum layer thickness: 15 nm [0095] Thickness of
the layer with chromium nanoparticle in chromium oxide: 20 to 30 nm
[0096] Base shade: red
Example C:
[0096] [0097] Aluminum layer thickness: 15 nm [0098] Thickness of
the layer with chromium nanoparticle in chromium oxide: 40 to 60 nm
[0099] Base shade: blue
[0100] According to a further variant of the invention, the
platelet-shaped metallic effect pigment has three or more layers
disposed one atop another, with at least one layer comprising metal
nanoparticles in a metal oxide phase, which comprises at least one
layer having a first and a second outer face, the metallic effect
pigment has a first outer face and a second outer face, and the
highest amount of metal nanoparticles is present in the first or in
the second outer face of the metallic effect pigment, and the
amount of metal nanoparticles in the first and in the second outer
face of the at least one layer differs by at least 10 atom %.
[0101] In accordance with the invention it is also preferred for
the amount of metal nanoparticles, in at least one layer which
comprises metal nanoparticles and metal oxide phase, to alter
continuously over the thickness of that layer.
[0102] In at least one layer which comprises metal nanoparticles
and metal oxide phase, the amount of metal nanoparticles preferably
changes at least partly with a gradient which is in a range from
0.1 to 4 atom %/nm over the thickness of the layer. According to a
further-preferred variant, the gradient is in a range from 0.5 to 3
atom %/nm.
[0103] According to a further-preferred variant, the amount of
metal nanoparticles changes discontinuously between two successive
layers. According to one preferred variant of the invention, the
difference in the amount of metal nanoparticles is in a range from
10 atom % to 40 atom %, more preferably from 12 atom % to 35 atom
%, and more preferably still from 15 atom % to 30 atom %.
[0104] In a further preferred variant of the layer of the invention
in which metal nanoparticles are present in a metal oxide matrix,
the average amount of metal M and oxygen is at least 80 atom %,
more preferably at least 90 atom %, based on this one layer. This
layer may therefore also contain extraneous elements and/or
extraneous atoms. Preferred extraneous elements in this layer are,
for example, nitrogen, sulfur, carbon and/or hydrogen. Thus, more
particularly, nitrogen (preferably in the form of metal nitrides)
may be incorporated into the layer if air is used as the oxygen
source when producing the metallic effect pigments of the
invention.
[0105] The visual impression given by the metallic effect pigments
may therefore be influenced by a multiplicity of possible
combinations. Thus, for example, the metallic luster of the
metallic effect pigments of the invention can be intensified by
forming an outer face of the metallic effect pigment by means of a
metallic layer. A metallic layer is therefore to be understood as a
layer which is formed substantially, preferably completely, from
continuous metal, which superficially may also have a naturally
occurring metal oxide layer. In this layer of continuous metal
there are therefore no metal nanoparticles present in a metal oxide
matrix.
[0106] According to a further variant of the invention, the
metallic effect pigment has at least one first and one second
successive layer, the first layer comprising metal nanoparticles
and the second layer comprising elemental metal, the amount of
metallic nanoparticles in the outer face of the first layer, which
comprises metal nanoparticles and metal oxide phase, being in a
range from 1 to 50 atom %, and the amount of elemental metal in the
outer face of the second layer being in a range from 60 to 95 atom
%, with the proviso that the difference in the amount of metal
nanoparticles and of elemental metal in the two outer faces is at
least 10 atom %.
[0107] With this variant, the metallic effect pigments of the
invention have a metal layer which is able to act as a reflector.
It is of course also possible to dispose the metal layer centrally,
so that at least one layer comprising metal nanoparticles in a
metal oxide layer is disposed respectively on the top face and on
the bottom face of the metal layer.
[0108] The average amount of metal in the metal layer, based on the
total amount of metal and oxygen in this at least one layer, is in
a range from 60 to 95 atom %. With further preference the average
amount of metal and oxygen in the at least one layer is at least 90
atom %, preferably at least 95 atom %, and more preferably at least
97 atom %, based in each case on this one layer. In this metal
layer there are therefore no metal nanoparticles present. Instead,
this metal layer is a conventional metal layer, which may also
comprise metal oxide.
[0109] In the case of the above variant of the invention, the metal
is preferably a trivalent metal and more preferably the metal is
selected from the group consisting of aluminum, chromium, and
mixtures and alloys thereof.
[0110] In another variant it is preferred for the metal to be a
tetravalent metal and with particular preference to be selected
from the group consisting of titanium, tin, and mixtures and alloys
thereof. In this case the metallic effect pigment has at least one
first and one second successive layer, the first layer comprising
metal nanoparticles and the second layer comprising elemental
metal, and the amount of metal nanoparticles in the outer face of
the first layer, which comprises metal nanoparticles and metal
oxide phase, being in a range from 1 to 50 atom %, and the amount
of elemental metal in the outer face of the second layer being in a
range from 60 to 95 atom %, with the proviso that the difference in
the amount of metal nanoparticles and of elemental metal in the two
outer faces is at least 10 atom %.
[0111] With this variant of the metallic effect pigments of the
invention as well, the metal layer may act as a reflector. It is of
course possible here as well for the metal layer to be arranged
centrally, so that at least one layer comprising metal
nanoparticles in a metal oxide layer is disposed respectively on
the top face and on the bottom face of the metal layer.
[0112] In accordance with one preferred development of the
invention, the at least one layer which comprises metal
nanoparticles and metal oxide phase has an average oxygen content
of 15 to 77 atom %, based on the total amount of metal and oxygen
in this layer.
[0113] In the case of further-preferred embodiments, the layer has
an average oxygen content of 30 to 57 atom %, more preferably of 35
to 53 atom %.
[0114] According to a preferred embodiment of the invention, the
oxygen content in the case of monovalent metals is in a range from
15 to 30, preferably from 20 to 28 atom %.
[0115] According to one preferred embodiment of the invention, the
oxygen content in the case of divalent metals is in a range from 28
to 48, preferably from 33 to 43 atom %.
[0116] According to one preferred embodiment of the invention, the
oxygen content in the case of trivalent metals is in a range from
30 to 58, preferably from 35 to 53 atom %.
[0117] According to one preferred embodiment of the invention, the
oxygen content in the case of tetravalent metals is in a range from
40 to 64, preferably from 45 to 59 atom %.
[0118] The oxygen present in this layer is in the form of metal
oxide. This metal oxide forms a matrix into which the metal
nanoparticles have been incorporated. The metal oxide matrix
produces a number of advantages. First, it protects the
oxidation-sensitive metal nanoparticles, entirely surprisingly,
against oxidation, very effectively. This is a very surprising
effect for the reason in particular that metallic nanoparticles are
known to be significantly more base and hence more susceptible to
corrosion than their macroscopic embodiments.
[0119] Secondly, the metal oxide matrix endows the layer with
mechanical properties which are barely distinguishable from the
properties of corresponding conventional metal oxides. The layers
of the invention are therefore likewise mechanically brittle, which
has the great advantage that the metallic pigments of the invention
can be comminuted mechanically with great ease. This leads to
metallic effect pigments whose fracture edges have a pronounced
smoothness, and this in turn is very conducive to the optical
properties (flop, luster).
[0120] The at least one layer in this case consists essentially of
metal and oxygen. The metal here is present on the one hand as
elemental metal, in the form of metal nanoparticles, and on the
other hand as metal oxide. The metal, and therefore the metal
nanoparticles and/or the metal in the metal oxide matrix, may also
in each case be a mixture of different metals, with the mixture of
different metals in the metal nanoparticles and in the metal oxide
matrix being identical.
[0121] On account of the specific structure of the layer of metal
nanoparticles and metal oxide matrix, the layer of the invention
differs, significantly from purely stoichiometric or else
nonstoichiometric metal oxide layers. In optical terms, the layer
of the invention produces a metallic appearance with a high
light/dark flop. Depending on the size and/or on the concentration
of the metal nanoparticles and/or on the layer thickness, it is
also possible at the same time for a dark to black coloration to
occur. Effect pigments based on this layer are therefore perceived
optically as metallic effect pigments. In terms of their mechanical
properties, however, the metallic effect pigments of the invention
equate more to typical pearlescent pigments based on metal
oxides.
[0122] In accordance with the invention, in the case of a further
variant of the invention, it is preferred for the metallic effect
pigment to comprise at least three layers:
A) a layer A which has at least one metal M.sub.A and an average
oxygen content O.sub.A, based on the total amount of M.sub.A and
O.sub.A in the layer A, B) a layer B with at least one metal
M.sub.B and an average oxygen content O.sub.B of 0 to 77 atom %,
based on the total amount of M.sub.B and O.sub.B in the layer B, C)
a layer C which has at least one metal M.sub.C and an average
oxygen content O.sub.C, based on the total amount of M.sub.C and
O.sub.C in the layer C, the average oxygen content O.sub.AC in the
layers A and C being determined in accordance with the formula
(I)
O AC = 1 2 ( O A M A + O A + O C M C + O C ) ( I ) ##EQU00001##
and being in a range from 8 to 77 atom %, with the proviso that at
least one of the layers, A, B, or C, comprises metal
nanoparticles.
[0123] According to a further variant of this embodiment, the
average amount of oxygen O.sub.AC in the layers A and C is in a
range from 10 to 74 atom %, more preferably from 15 to 70 atom %,
more preferably still in a range from 20 to 64 atom %. The amounts
are based in each case on the total amount of M.sub.A, O.sub.A,
M.sub.C, and O.sub.C in the layers A and C.
[0124] According to a further preferred embodiment, the average
amount of oxygen O.sub.A, based on the total amount of M.sub.A and
O.sub.A in the layer A, and the average amount of oxygen. O.sub.C,
based on the total amount of M.sub.C and O.sub.C in the layer C,
are independently of one another each in a range from 25 to 58 atom
%, preferably from 30 to 57 atom %.
[0125] In the case of monovalent metals, the average amount of
oxygen O.sub.AC in the layers A and C is preferably in a range from
8 to 30 atom %. In the case of divalent metals the amount of oxygen
O.sub.AC is preferably in a range from 25 to 48 atom %. In the case
of trivalent metals the amount of oxygen O.sub.AC is preferably in
a range from 30 to 58 atom %. In the case of tetravalent metals the
amount of oxygen O.sub.AC is preferably in a range from 35 to 64
atom %.
[0126] According to yet a further variant of the invention, the
total amount of M.sub.A and of O.sub.A in the layer A of the
metallic effect pigment is 80 to 100 atom %, based on all of the
components in the layer A.
[0127] According to yet a further variant of the invention, the
total amount of M.sub.C and of O.sub.C in the layer A of the
metallic effect pigment is 80 to 100 atom %, based on all of the
components in the layer C.
[0128] According to yet a further variant of the invention, in the
layer A and the layer C of the metallic effect pigment, the total
amount of M.sub.A and of O.sub.A is 80 to 100 atom % and the total
amount of M.sub.C and O.sub.C is 80 to 100 atom %, based in each
case on all of the components in the layer A and C,
respectively.
[0129] According to one extremely preferred embodiment of the
invention, in the above-described variants of a metallic effect
pigment comprising at least three layers, the metal is selected
from the group consisting of aluminum, chromium, and mixtures and
alloys thereof.
[0130] In one preferred use of aluminum as metal, it is possible to
provide metallic effect pigments which have, for example, a
gold-colored base shade in addition to the rainbow effect.
[0131] The metallic effect pigments of the invention can be used
for example in cosmetics. Cosmetics are subject to very stringent
provisions with regard to allowable ingredients. Heavy metals must
not be used in the production of cosmetics. Accordingly, the
provision of heavy-metal-free metallic effect pigments with rainbow
effect and an adjustable base shade is a great advantage in the
cosmetics industry, for example, but also in the paint, ink, or
plastics industries.
[0132] According to a further variant of the invention, the metal
effect pigment is enveloped with an anticorrosion layer which is
optionally surface-modified.
[0133] The metallic effect pigments of the invention may be
provided with a protective layer, preferably an enveloping
protective layer, against corrosion. This protective layer may
comprise or consist of metal oxide and/or plastic.
[0134] According to one preferred embodiment of the invention, the
metal oxide layer has been applied using sol-gel methods. The metal
oxide is preferably silicon oxide, aluminum oxide, cerium oxide, or
mixtures thereof.
[0135] In a further variant of the invention, the metallic effect
pigments of the invention have been provided with a plastics layer.
The layer in question is preferably a polyacrylate and/or
polymethacrylate layer.
[0136] It is of course also possible for mixed layers of metal
oxide and plastic to be applied. Also possible is a sequential
arrangement, in which the layer or layers of plastic and the layer
or layers of metal oxide are disposed in succession.
[0137] According to one preferred variant of the invention a
silicon oxide layer, preferably SiO.sub.2 layer, is used as
anticorrosion layer. The silicon oxide layer has been applied
preferably by means of sol-gel methods, in which case preferably
tetraalkoxysilanes, in the case of a first variant under acidic or
basic conditions in a one-stage process, or, in the case of a
second variant, initially under acidic and then under basic
conditions, in a two-stage process, or in the case of a third
variant, initially under basic conditions and then under acidic
conditions, in a two-stage process, are hydrolyzed, and silicon
oxide, preferably SiO.sub.2, is deposited on the metallic effect
pigment of the invention. The tetraalkoxysilanes are preferably
tetramethoxysilane, tetraethoxysilane and/or
tetraproppxysilane.
[0138] It is of course also possible for the metal oxide layer to
have been applied by hydrolysis of metal salts, such as metal
halides, for example, preferably metal chlorides.
[0139] According to another preferred embodiment, the metal oxide
layer, preferably silicon oxide layer, is organochemically
modified. This organochemical surface modification may involve
hydrophobizing agents, such as alkylsilanes, for example. It is
also possible, however, for reactive surface modifiers to have been
disposed that have reactive functional organic groups. These
reactive functional organic groups may be acrylic, methacrylic,
vinyl, epoxide, hydroxyl, amino, mercapto groups, etc. Via these
reactive functional groups there is a possibility of chemical
attachment--for example, to the binder or binders of an ink,
printing-ink, paint, or plastic. As a result of the chemical
attachment, the metallic effect pigments are incorporated more
effectively, and so the corrosion resistance of the metallic effect
pigments and/or the condensation resistance of a paint are
significantly enhanced.
[0140] The metallic effect pigments of the invention are obtained
using physical vapor deposition (PVD).
[0141] This process encompasses the following steps:
(a1) applying a release layer to a linearly movable substrate, (a2)
introducing a diffractive structure into the release layer,
preferably by embossing, (a3) applying at least one metal to the
release layer on the linearly movable substrate, in a vacuum
chamber having a vapor-deposition section, by means of reactive
physical vapor deposition (PVD), in the presence of oxygen, or (b1)
applying a release layer to a linearly movable substrate, (b2)
applying at least one metal to the release layer on the linearly
movable substrate, in a vacuum chamber having a vapor-deposition
section, by means of reactive physical vapor deposition (PVD), in
the presence of oxygen, (b3) introducing a diffractive structure
onto and/or into at least one surface of the PVD layer applied in
step (b2), preferably by embossing, and also c) detaching the
applied PVD layer(s) provided with a diffractive structure, d)
comminuting the detached PVD layer(s), e) optionally transferring
the comminuted PVD layer(s) into a dispersion or paste.
[0142] "Reactive physical vapor deposition" refers, in accordance
with the invention, to the deposition of metal vapor in the
presence of oxygen, as for example pure oxygen or air, or an
oxygen-donating source, as for example water. In the course of this
reactive physical vapor deposition (PVD), metal oxide and metal, in
the form for example of metal nanoparticles, are deposited.
[0143] The reactive physical vapor deposition is carried out
preferably under a pressure in a range from 1.times.10.sup.-5 to
1.times.10.sup.-2 mbar, preferably from 1.times.10.sup.-4 to
1.times.10.sup.-3 mbar. In order to bring about effective
conversion of metal vapor and oxygen, the oxygen is supplied under
a lower pressure preferably closer to the metal vapor source than
at a higher pressure.
[0144] For the production of the metallic effect pigments of the
invention there are two possible approaches, which differ in terms
of the formation of the diffractive structure.
[0145] In the case of the first approach, the release layer, also
referred to as "release coat", which is applied to the linearly
movable substrate, typically a polymeric film, as for example a
polyester film, is provided with a diffractive structure and then
the metal is vapor-coated on.
[0146] In the case of the second approach, a release layer is
applied to the linearly movable substrate, typically a polymeric
film, as for example a polyester film, and the metal is then
vapor-coated onto said release layer. After the film of metal has
been applied, the diffractive structure is then introduced into the
film of metal.
[0147] The diffractive structure may be introduced for example by
embossing into the release layer or into the applied film of metal.
Embossing may take place, for example, using an embossing die or an
embossing roll. In this case, a negative impression of the
embossing die or of the embossing roll is introduced into the
release layer or into the applied metal layer.
[0148] In terms of the embossing patterns, reference is made to the
above observations concerning the embossed or shaped metallic
effect pigments. The observations apply correspondingly.
[0149] Vapor deposition with metal may take place in a conventional
way, as for example by means of electron beam technology,
sputtering, or resistance-heated and/or radiation-heated methods.
It is possible here for two or more evaporators to be disposed in
series and/or in parallel with one another.
[0150] The thickness of the metal layers can be checked by means of
transmission measurements. Owing to the partially oxidic nature of
the film layer, the transmissions are usually lower than for the
evaporation of pure metals.
[0151] When generating colored oxide layers, which are applied to a
reflective metal layer, for example, it is also possible to employ
reflection measurements for the purpose of controlling or
regulating the evaporation procedure.
[0152] The oxygen or oxygen donor that is supplied during the vapor
deposition step can be introduced by means of a multiplicity of
possible procedural variants into the vacuum chamber that is used
for the vapor deposition. In general the oxygen is regulated using
mass flow controllers and is metered into the vacuum chamber in the
desired positioning.
[0153] The oxygen source, for example oxygen or the oxygen donor,
for example water or water vapor, can be introduced into the vacuum
chamber directly and centrally, or diffusely and with homogeneous
distribution in the metal vapor, or at a distance from the metal
vapor source.
[0154] By central disposition of metal vapor source and oxygen
source, or by diffuse addition of the oxygen source, it is possible
to produce a layer featuring homogeneously distributed metal
nanoparticles in a metal oxide matrix.
[0155] Diffuse addition means an addition where the oxygen source
is introduced into the vacuum chamber in such a way that in the
vacuum chamber no gradient is produced in terms of the oxygen
source, and therefore the distribution of the oxygen source in the
vacuum chamber is homogeneous.
[0156] Both with a central disposition of metal vapor and oxygen
supply and with diffuse addition of the oxygen source, a
homogeneous distribution of the metal nanoparticles in the metal
oxide phase or metal oxide layer is produced.
[0157] If the metal vapor source is at a spatial distance from the
oxygen source in relation to the direction of movement of the
substrate to be vapor-coated, there is a superimposition of a metal
vapor with a radially falling metal vapor concentration, and there
is an oxygen source, oxygen gas for example, with radially
decreasing concentration and for the purpose of generating a layer
on the substrate having a metal nanoparticle gradient in a metal
oxide matrix.
[0158] In the case of decentralized arrangement of the oxygen
supply in relation to the metal vapor source, therefore, a gradient
of metal nanoparticles in a metal oxide phase or metal oxide matrix
is produced. If the oxygen supply is arranged before the metal
vapor source in relation to the direction of movement of the
linearly moved substrate, a belt for example, then more metal oxide
and fewer metal nanoparticles are deposited at the beginning.
Subsequently, in the direction of movement of the substrate, there
is an increase in the fraction of metal nanoparticles and a
decrease in the fraction of metal oxide.
[0159] If the oxygen supply, relative to the direction of movement
of the substrate, is arranged after the metal vapor source, then
initially more metal nanoparticles and less metal oxide are
deposited. Subsequently, in the direction of movement of the
substrate, there is a decrease in the fraction of metal
nanoparticles and an increase in the fraction of metal oxide.
Through the disposition of the metal vapor source at a distance
from the oxygen supply or oxygen source, therefore, it is possible
to generate a gradient of metal nanoparticles in a metal oxide
phase or metal oxide matrix.
[0160] Depending on the distance of the oxygen supply disposition
relative to the metal vapor source, the metal oxide content can
also go down to zero, meaning that a pure metal layer is applied as
one of the two outer faces of the metallic effect pigment. It is
therefore possible to apply a two-layer metallic effect pigment of
the invention in a single-stage process. The first layer in this
case comprises a gradient of metal nanoparticles in a metal oxide
layer, with an increase in the relative fraction of metal
nanoparticles, a decrease in the relative proportion of metal
oxide, and, lastly, a continuous metal layer, which acts as an
absorber or reflector depending on the layer thickness, is
applied.
[0161] The present invention therefore relates to processes by
which it is possible to produce metallic effect pigments of the
invention in which the at least one layer which comprises metal
nanoparticles in a metal oxide phase or metal oxide matrix has a
homogeneous construction or a gradient.
[0162] According to a further variant, therefore, the present
invention relates to a process for providing metallic effect
pigments which at least one layer of substantially homogeneous,
preferably homogeneous, construction, comprising metal
nanoparticles and metal oxide phase or metal oxide matrix, with the
following steps: [0163] (a1) applying a release layer to a linearly
movable substrate, [0164] (a2) introducing a diffractive structure
into the release layer, preferably by embossing, [0165] (a3)
vaporizing a linearly moved substrate, in a vacuum chamber having a
vaporizing section, by means of reactive physical vapor deposition
(PVD), with at least one metal in the presence of oxygen, so that
part of the metal reacts with oxygen to form metal oxide, and
unreacted metal in the form of metal nanoparticles, and formed
metal oxide, are deposited via the vaporizing section in
substantially homogeneous, preferably homogeneous, distribution in
relation to the direction of movement of the linearly moved
substrate, to give a PVD layer or a plurality of PVD layers
disposed one atop another, [0166] or [0167] (b1) applying a release
layer to a linearly movable substrate, [0168] (b2) vaporizing a
linearly moved substrate, in a vacuum chamber having a vaporizing
section, by means of reactive physical vapor deposition (PVD), with
at least one metal in the presence of oxygen, so that part of the
metal reacts with oxygen to form metal oxide, and unreacted metal
in the form of metal nanoparticles, and formed metal oxide, are
deposited via the vaporizing section in substantially homogeneous,
preferably homogeneous, distribution in relation to the direction
of movement of the linearly moved substrate, to give a PVD layer or
a plurality of PVD layers disposed one atop another, [0169] (b3)
introducing a diffractive structure onto and/or into at least one
surface of the PVD layer applied in step (b2), preferably by
embossing, and also [0170] (c) detaching the applied PVD layer(s)
provided with a diffractive structure, [0171] (d) comminuting the
detached PVD layer(s), [0172] (e) optionally transferring the
comminuted PVD layer(s) into a dispersion or paste.
[0173] According to a further variant, additionally, the present
invention relates to a process for providing metallic effect
pigments which at least one gradient layer, comprising metal
nanoparticles and metal oxide phase or metal oxide matrix, with the
following steps: [0174] (a1) applying a release layer to a linearly
movable substrate, [0175] (a2) introducing a diffractive structure
into the release layer, preferably by embossing, [0176] (a3)
applying at least one metal to the release layer on the linearly
moved substrate, in a vacuum chamber having a vaporizing section,
by means of reactive physical vapor deposition (PVD) in the
presence of oxygen, so that part of the metal reacts with oxygen to
form metal oxide, and unreacted metal in the form of metal
nanoparticles, and formed metal oxide, are deposited via the
vaporizing section with formation of a gradient in relation to the
direction of movement of the linearly moved substrate, to give a
PVD layer or a plurality of PVD layers disposed one atop another,
[0177] or [0178] (b1) applying a release layer to a linearly
movable substrate, [0179] (b2) applying at least one metal to the
release layer on the linearly moved substrate, in a vacuum chamber
having a vaporizing section, by means of reactive physical vapor
deposition (PVD) in the presence of oxygen, so that part of the
metal reacts with oxygen to form metal oxide, and unreacted metal
in the form of metal nanoparticles, and formed metal oxide, are
deposited via the vaporizing section with formation of a gradient
in relation to the direction of movement of the linearly moved
substrate, to give a PVD layer or a plurality of PVD layers
disposed one atop another, [0180] (b3) introducing a diffractive
structure onto and/or into at least one surface of the PVD layer
applied in step (b2), preferably by embossing, and also [0181] (c)
detaching the applied PVD layer(s) provided with a diffractive
structure, [0182] (d) comminuting the detached PVD layer(s), [0183]
(e) optionally transferring the comminuted PVD layer(s) into a
dispersion or paste.
[0184] According to a further variant of the invention, the process
encompasses the following steps: [0185] (a1) applying a release
layer to a linearly movable substrate, [0186] (a2) introducing a
diffractive structure into the release layer, preferably by
embossing, [0187] (a3) sequential application of layers A, B, and C
one atop another by means of physical vapor deposition, by vapor
application of metals M.sub.A, and M.sub.C onto a linearly moved
substrate, with at least the layers A and/or C being applied in the
presence of at least one oxygen-donating oxygen source and where,
correspondingly, the substrate for the layer A and/or B has a
release layer with a diffractive structure, [0188] or [0189] (b1)
applying a release layer to a linearly movable substrate, [0190]
(b2) sequential application of layers A, B, and C one atop another
by means of physical vapor deposition, by vapor application of
metals M.sub.A, M.sub.B, and M.sub.C onto a linearly moved
substrate, with at least the layers A and/or C being applied in the
presence of at least one oxygen-donating oxygen source and where,
correspondingly, the substrate for the layer A and/or B has a
release layer with a diffractive structure, [0191] (b3) introducing
a diffractive structure onto and/or into at least one surface of
the PVD layer applied in step (b2), preferably by embossing, and
also [0192] (c) detaching the applied PVD layer(s), [0193] (d)
comminuting the detached PVD layer(s), [0194] (e) optionally
transferring the comminuted PVD layer(s) into a dispersion or
paste.
[0195] For the generation of a substantially homogeneous
distribution of the metal nanoparticles in an oxidic matrix, there
are a number of possible variants.
[0196] In the case of metal vaporization, using for example a
vaporizer crucible (10), as illustrated in FIGS. 2 to 6, a region
with very high metal density, this density decreasing radially, is
produced centrally above the vaporizer--for example, vaporizer
crucible (10).
[0197] The oxygen source, oxygen for example, may be admitted to
the vacuum chamber (1) diffusely, via the oxygen inlet (15), as
illustrated in FIG. 2. The metal vapor or metal oxide is then
deposited on the linearly moved substrate (14), which is supplied
through the shutter entrance (11) via a source roll (3) and a
deflecting roll (4). The vapor-coated substrate is subsequently
supplied via the shutter exit (12) and the deflecting roll (5) to
the pickup roll (6). Located between the shutter entrance (11) and
shutter exit (12) is the vaporizing section (13), in which the
substrate (14) is vapor-coated. The process of deposition on the
substrate (14) is monitored by means of transmission measurement
(7; 8).
[0198] FIG. 3 shows a simplified apparatus for implementing the
process of the invention. The oxygen source, oxygen for example, is
admitted diffusely into the vacuum chamber via the gas inlet 20.1.
The vaporizer crucible (10) is disposed beneath the substrate on
which vapor coating is to take place. The vaporizing section (13)
is defined by the cover plate (18) at the shutter entrance (16) and
by the cover plate (19) at the shutter exit (17).
[0199] This simple variant can be used, for example, for producing
very thin metal layers having a thickness of less than 30 nm. It is
preferred here to produce metal nanoparticle-containing metal oxide
layers of titanium, aluminum, and/or chromium.
[0200] The homogeneity of the layers can be improved by a slightly
reduced rate of metal vaporization, since the oxygen then disperses
more readily into the metal vaporization cone that forms.
[0201] In order to generate layer thicknesses higher than 30 nm,
preferably 40-50 nm, the oxygen can also be introduced into the
vaporizing cone in a more targeted way, through laterally disposed
oxygen lances (20.2, 20.3, 20.4) with corresponding openings, as is
shown in FIGS. 4, 5, and 6. Supply via lateral oxygen lances (20.2,
20.3, 20.4) may take place unilaterally (FIGS. 4 and 6) or
bilaterally (FIG. 5).
[0202] The coated substrates, typically foils, exhibit an initially
dark gray transparent, slightly color-tinged appearance in the case
of oxygen contents, for Al and Cr, of 40-55 atom %.
[0203] Following detachment and comminution of the film that has
been applied by vapor deposition, the respective color effect of
the pigment comes about in an application, since a plurality of
pigments are present atop one another and give a uniform perceived
color.
[0204] Another advantageous variant is to supply the oxygen or the
oxygen source directly above the vaporizing crucible (10) or
vaporizing boat in the case of very high metal vaporization rates.
This is also shown, by way of example, in FIGS. 4 and 6.
[0205] For optimum conversion of the metal, particular suitability
is possessed by the geometry shown in FIG. 6, since both the oxygen
or oxygen source and the vaporized metal are supplied centrally and
are converted in dependence on the amount of oxygen prior to
deposition on the moved substrate.
[0206] In order to produce metallic effect pigments of the
invention where the amount of metal differs by at least 10 atom %
between the at least one layer comprising metal nanoparticles and
metal oxide phase or metal oxide matrix and a second layer, it is
possible to carry out vapor deposition on a commercial metal
reflector foil, an example an aluminum foil having a layer
thickness in a range of preferably from 10 nm-50 nm. The aluminum
foil can be provided with a diffractive structure by embossing
prior to vapor deposition. Here, in accordance with one preferred
variant, oxidically embedded metal nanoparticles of Cr, Ti and/or
Al are applied, and in interaction with the metal reflector, for
example aluminum reflector or aluminum layer, may produce a blue
appearance on the coated foil. Particularly advantageous for a blue
coloration on an aluminum reflector (aluminum foil) is a layer
thickness of oxidically embedded metal nanoparticles of Cr, Al, or
Ti of around 60 nm.
[0207] Detachment and comminution of the film produces metallic
effect pigments of the invention which are notable first for a
strong metallic effect and secondly for a slight bluish tinge. The
diffractive structure of the metallic effect pigments gives the
metallic effect pigments a high-grade metallic, blue-tinged
appearance with a rainbow.
[0208] Metallic effect pigments of the invention which contain a
metal nanoparticle gradient in a metal oxide matrix can be
produced, for example, with an apparatus which is shown in FIG. 5,
where the oxygen source, oxygen for example, takes place only
unilaterally, i.e., via the left-hand or right-hand gas inlet shown
in FIG. 5.
[0209] An advantage in the case of this process variant is that the
procedure can be controlled via reflection measurements, since a
preferably blue coating is generated on a metallic reflector.
[0210] The extent of the rainbow effect can be influenced in this
case by the diffractive structure embossed into the foil. In the
case of embossed foils which have embossing only partially, the
metallic luster, for example, is enhanced, and the rainbow effect
is established in a restrained manner in the end application, in a
paint or an ink.
[0211] In a further preferred embodiment, the metallic effect
pigments of the invention have a three-layer construction, with the
metals M.sub.A, M.sub.B, and M.sub.C in the layers A, B, and C
being the same and being preferably aluminum. With the apparatus
depicted in FIG. 6 it is possible to provide gold-colored embossed
effect pigments in a simple way.
[0212] In the case of this variant, oxygen is supplied to the metal
vaporization cone centrally via the vaporizer.
[0213] An advantageous feature of this process variant is that, for
a supplied defined amount of oxygen or amount of metal vapor per
unit time, it is possible to produce gold-colored embossed metallic
effect pigments, i.e., pigments with a diffractive structure, with
different layer thicknesses. The layer thicknesses here can be
controlled via the set speed of the substrate, typically a
polymeric film. When using aluminum as metal M.sub.A, M.sub.B/and
M.sub.C here, a "gold range" is established for layer thicknesses
of 30 nm to 250 nm, preferably of 50 nm to 150 nm, more preferably
of 70 nm to 100 nm. The oxygen fraction in the case of these
metallic effect pigments, in all of layers A, B, and C, is
preferably between 30 and 35 atom %.
[0214] Accordingly, this process can also be utilized in a simple
way in order to reduce the size of the metal nanoparticles, by
means of further supply of oxygen gas, and, with different layer
thicknesses, to generate dark to black pigments. There is a "black
range" here for layer thicknesses of 15 nm to 250 nm, preferably of
30 nm to 150 nm, more preferably of 50 nm to 100 nm. In this
variant of the metallic effect pigments, the oxygen fraction in all
of layers A, B, and C is preferably in a range between 45 and 55
atom %.
[0215] A further preferred embodiment, in which the metal M.sub.B
is different from the metals M.sub.A and M.sub.C, represents the
sequence of the vaporized metal with Cr/Al/Cr.
[0216] Metallic effect pigments of the invention that have this
construction are notable for a particular corrosion resistance. The
external chromium and/or chromium oxide layers protect the
centrally disposed thin aluminum oxide layer, which contains
aluminum nanoparticles and has a layer thickness, for example, in a
range from 15 to 25 nm, effectively against corrosion. Commercial
silver-colored pigments in this layer thickness range are found not
to be resistant in corresponding QUIZ and chemicals testing.
[0217] One particularly preferred embodiment here is a highly
lustrous embossed pigment. The layer thicknesses of the layers A
and C, which comprise chromium nanoparticles in chromium oxide, are
in a range from 15 to 20 nm, and the oxygen content is between 35
to 58 atom %, preferably from 40 to 45 atom %. In this embodiment
the layer B is a PVD aluminum layer which has not been applied by
vapor deposition under reactive conditions. This aluminum layer may
comprise aluminum oxide on the surface. The core of this aluminum
layer consists of metallic aluminum which is not present in the
form of aluminum nanoparticles. The layer thickness of the layer B
is in a range from 15 to 50 nm, preferably from 20 to 30 nm.
[0218] A particularly advantageous circumstance here is that,
because of the low layer thicknesses of the chromium oxide layer,
comprising chromium nanoparticles, it is possible to carry out
coating at the same belt speeds as in the case of coating with the
aluminum layer. Typical belt speeds here may be 800 m/min or even
higher. The metering of oxygen into a thin Cr layer of 15 nm can be
accomplished in a simple way via a diffuse oxygen inlet as per FIG.
3.
DESCRIPTION OF THE FIGURES
[0219] FIG. 1 shows the schematic construction of a metallic effect
pigment of the invention with an embossed surface, with metal
nanoparticles present in an oxidic matrix.
[0220] FIG. 2 shows the construction of a PVD apparatus in a vacuum
chamber 1, in the form of a belt coating unit having a source roll
3, from which the linearly moving substrate 14 is unrolled. The
substrate is then guided via the deflecting rolls 4 and 5 to the
pickup roll 6. The shutters 11 and 11.1 and 12 and 12.1 represent
the coating chamber. The shutters 11 and 12 delimit the vaporizing
section 13, in which the linearly moved substrate is vapor-coated
by means of PVD. The shutters 11.1 and 12.1 separate the vaporizing
unit with vaporizer crucible 10 from the surroundings. The
transmission measurement 7 and 8 or oscillating quartz measurement
9 allow the amount of deposited metal oxide and elemental metal to
be ascertained.
[0221] FIGS. 3 to 6 show particular embodiments of the apparatus
illustrated in FIG. 2.
[0222] FIG. 3 shows an alternative construction in the region
confined in section 2 of FIG. 2, with a left-hand cover plate 16
(11 and 11.1) for the entry of the foil/film into the coating
chamber, and with a right-hand cover plate for the exit 17 of
foil/film (12 and 12.1) from the coating chamber. The coating
region of the substrate is further bounded by the cover plates 18
and 19. Outside of the section 2 there is a small aperture for an
optional diffuse gas inlet indicated in the left-hand vacuum
chamber wall 15.
[0223] FIG. 4 shows an alternative construction in the region
confined in section 2 of FIG. 2. The gas supply is through a
horizontal gas inlet tube 20.2 drawn in centrally above the
vaporizer crucible 10 with three small apertures each with a
diameter of around 1 mm. The outflow apertures are indicated by
three small arrows.
[0224] FIG. 5 shows an alternative construction in the region
confined in section 2 of FIG. 2, having an upper coating section
13.1 and a lower coating section 13.2. The upper coating section
13.1 is bounded by the apparatus 16 and 19. The lower coating
section 13.2 is described through the lower left-hand cover plate
18.1 and a right-hand lower cover plate 19.1. The supply of gas
through a right-hand/left-hand gas inlet tube, each with three
small openings with a diameter of approximately 1 mm in each case,
from each side. The outflow openings are indicated by small
arrows.
[0225] FIG. 6 shows an alternative construction in the region
bounded by section 2 of FIG. 2, where the supply of gas 18 realized
with a gas inlet through a tube 20.4, which is vertical in the
direction of vaporization, and with an opening of approximately 4
mm. The vertical tube is located on an axis with the vaporizer
crucible 10.
[0226] FIG. 7 shows the plan view of the arrangement of the
shutters, for generating a sequential layer construction on the
substrate, which moves at a constant belt speed, for example 7 and
for comparative example 7. The longitudinal shutters here, 21,
22.1, and 22.2 and 23, confine the coating regions for examples 7a,
7b, and 7c and for comparative examples 7a, 7b, and 7c,
respectively.
[0227] FIG. 8 shows a TEM image of the PVD layer from example 1.
The dark patches are metal nanoparticles.
[0228] FIG. 9 shows the electron diffraction image associated with
FIG. 8 of the PVD layer from example 1. The diffraction reflections
are arranged in concentric rings. The zero-order reflection is
blanked out. The concentric rings show that the black patches from
FIG. 8 are metal nanoparticles.
[0229] FIG. 10 represents the intensity distribution of the
electron diffraction reflections of the oxidic aluminum layers from
inventive example 1. The plot is of reflection intensity against
reciprocal lattice spacing.
[0230] FIGS. 11a and 12a each show concentration distributions,
determined by means of xPS/ESCA sputter profiles, for the elements
oxygen (O), elemental metal (Al(0) or Ti(0), respectively), and
carbon (C) for the pigments of inventive example 4 and of
comparative example 4.
[0231] FIGS. 11b and 12b in each case represent the ratio of
elemental metal to oxidized metal in atom % over the layer
thickness, these figures corresponding to FIGS. 11a and 12a, but
without the oxygen fraction.
[0232] FIGS. 13a, 13b, and 13c show the colorimetric CIELAB data of
the L*, H* and C* data of the pigments from inventive example 1 and
from comparative examples 9, 9a, 9b, and 9c.
[0233] FIG. 13.d represents the spectral evaluation of the
colorimetry of the spectra of 12 .mu.m drawdowns of the pigments
from example 1 and from comparative examples 9, 9a, 9b, and 9c in
the visible wavelength range of in each case 400-700 nm at the
three measured specular angles of 25.degree., 45.degree., and
75.degree. in each case.
[0234] FIGS. 14a and 14b show the comparison of the H* profiles of
the CIELAB data of the pigments from inventive examples 1-6 and
from comparative examples 8 and 9 and comparative examples 1-6.
[0235] FIG. 15 shows the viewing direction 29 of a viewer around a
curved and illuminated knife application through the light sources
27.1, 27.2, and 27.3 in accordance with table 5. The appearance
generated to the observer as a result of the direction of viewing
at the reflection points 24, 25, and 26 is compiled in table 5.
[0236] FIG. 16 describes the geometric arrangement for the
colorimetric measurement of the drawdowns. The light source 30 here
shines constantly onto a surface 31 which is inclined at 45.degree.
and on which the respective drawdown is disposed.
[0237] FIG. 17 shows the amount of metal nanoparticle in a metallic
effect pigment in dependence on the oxygen content and on the
oxidation state of the metal.
[0238] FIG. 18 shows an SEM micrograph of the metallic effect
pigments of inventive example 1 in which the embossed frustoconical
structures are very visible.
EXAMPLES
[0239] In the text below, the production, characterization, and
colorimetric evaluation of the metallic effect pigments of the
invention are described with reference to inventive and comparative
examples, without imposing any restriction on the invention.
Part A: Production of the inventive metallic effect pigments with
reference to inventive examples 1-7 and comparative examples 1-7
and 8, which illustrate the prior art. Examples 1-7 (embossed) and
reference examples comp.--1-7 (unembossed) are produced
correspondingly by the coating process and therefore have the same
structural composition within the inventive pigments (examples 1-7)
and the pigments from the prior art (comp. examples 1-7). Part B:
Characterization of the structural composition of the inventive PVD
metallic effect pigments of inventive examples 1, 2, and 7c and of
comparative examples comp.--3a, comp.--4a, comp.--4b, comp.--8, and
comp.--9, on the basis of TEM measurements (transmitted light,
diffraction).
[0240] For further characterization, a commercial Metalure product,
comp. example 9, and an internally produced, silver-colored
Metalure type, comp. example 8, were investigated for their
structural composition.
Part C: Characterization of the structural composition of the
inventive pigments on the basis of EDX measurements--see substance
table 2. Part D: Characterization of the profile of oxygen and/or
metal over the layer thickness from the top face A to the bottom
face B on the basis of sputter profiles (elemental analysis ESCA
and statement of the oxidation states of the metal present in the
layer) for inventive examples 4 and comparative example 4. Part E:
Calorimetric evaluation of the inventive embossed PVD metallic
effect pigments. Part A: Preparation of the Inventive Metallic
Effect Pigments and Comparative Pigments in Accordance with
Inventive Examples 1-7 and Comparative Pigments 1-7 and 8
Step 1: Coating of the Carrier Film
[0241] The general production of the metallic effect pigments took
place in accordance with the process parameters in table 1.
[0242] For the individual examples and reference examples, a few
meters of an embossed film from the company CfC were additionally
spooled on in each case directly adjoining an already wound
unembossed film (source roll as per FIG. 2). The reference roll
used was an unembossed polyethylene terephthalate (PET) film having
a thickness of 23 .mu.m, coated with a release coat, as substrate.
The release coat consisted of acetone-soluble methyl methacrylate
resin and was applied conventionally beforehand in a separate
workstep.
[0243] The vaporization technique used was the electron-beam
vaporization technique.
[0244] Moreover, a distinction was made between a one-stage and a
two-stage, and also a three-stage, coating process.
[0245] The one-stage process describes the production of PVD
metallic effect pigments in accordance with the examples, with a
single coating step.
[0246] The two-stage process describes the production of PVD
metallic effect pigments in accordance with inventive examples, by
two separate, successive coating steps. The three-stage process
describes the production of PVD metallic effect pigments in
accordance with inventive examples, by three separate, successive
coating steps.
[0247] A constant coating rate of the layer thicknesses of the
vapor-deposited PVD metal layer and of the oxide incorporated
therewith on the substrate was monitored via the mass coverage
produced, by means of an oscillating quartz 9, located statically
in a vacuum chamber 1, and of an online transmission measurement 7
and 8, in accordance with FIG. 2.
[0248] The mass coverage produced on the substrate is determined
from the distance between substrate and metal vaporizer, the length
L of the shutter aperture, the belt speed of the substrate, and the
respective vaporization rate.
[0249] The gas flow required for the examples was supplied by means
of a gas flow regulator (mass flow controller) from the company
MKS, Munich, Germany. The location of the oxygen supply in each
case is shown schematically in FIGS. 3, 4, 5, and 6.
[0250] Mass coverage on the substrate was determined for the
examples by weighing following removal of the film.
[0251] A constant coating rate was ensured by means of an
oscillating quartz measurement 9 and an online transmission
measurement 7 and 8 in accordance with FIG. 2.
TABLE-US-00001 TABLE 1 Process parameters for the examples produced
Oxygen Chamber Mass Type of Patent Vaporized Vaporization Belt
speed amount vacuum coverage belt Substrate example substance
geometry [m*min.sup.-1] [sccm] [1*10.sup.-4 mbar] [g*m.sup.-1]
process Embossed 1 Al FIG. 5 32 500 1.7 0.076 One-layer 2 Cr FIG. 6
32 400 9 0.141 One-layer 3a Cr FIG. 3 24 300 2.5 0.055 3b Al FIG. 3
20 -- 0.9 0.1 3c Cr FIG. 3 24 300 1.38 0.117 3 0.272 Three-layer 4a
Al FIG. 3 20 -- 1.15 0.054 4b Ti FIG. 6 16 1100 3.95 0.207 4 0.276
Two-layer 5 Al FIG. 6 32 200 5.7 0.176 One-layer 6 Al FIG. 6 16 500
3.5 0.283 One-layer 7a Al FIG. 6 and 16 500 2 7b Al FIG. 7 7c Al 7
Al 0.324 One-layer Unembossed Comp. -1 Al FIG. 5 32 500 1.7 0.076
One-layer Comp. -2 Cr FIG. 6 32 400 9 0.141 One-layer Comp. -3a Cr
FIG. 3 24 300 0.055 Comp. -3b Al FIG. 3 20 -- 0.9 0.1 Comp. -3c Cr
FIG. 3 24 300 1.38 0.117 Comp. -3 0.272 Three-layer Comp. -4a Al
FIG. 3 20 -- 1.15 0.054 Comp. -4b Ti FIG. 6 16 1100 3.95 0.207
Comp. -4 0.276 Two-layer 5 Al FIG. 6 32 200 5.7 0.176 One-layer
Comp. -6 Al FIG. 6 16 500 3.5 0.283 One-layer Comp. -7a Al FIG. 6
and 16 500 2 Comp. -7b Al FIG. 7 Comp. -7c Al Comp. -7 Al 0.324
One-layer Embossed Comp. -8 Al FIG. 3 20 -- 1.1 0.121 One-layer
Step 2: Detachment from the Carrier Film and Comminution
[0252] Following physical vapor deposition, the individual PVD
layers or PVD layer stacks in accordance with the respective
examples were obtained from the carrier film by detachment with
solvent from the release-coated substrate. In the resultant
suspensions, residues of the release layer ("release coat") were
separated from the detached PVD layers or PVD layer packages using
solvent, and washed.
[0253] The external appearance generated by the coating process on
the pigments is indicated in table 3 following the detachment of
the pigments from the carrier layer.
[0254] The detached layers may be comminuted for example as
described in section E.
Part B:
[0255] Characterization of the Structural Composition of the
Inventive PVD Metallic Effect Pigments of Inventive Examples 1, 2,
and 7c and of Comparative Examples Comp.--3a, Comp.--4a, Comp.--4b,
Comp.--8, and Comp.--9, on the Basis of TEM Measurements
(Transmitted Light, Diffraction).
[0256] For further characterization, a commercial Metalure type,
comp. example 9, and an internally produced, silver-colored
Metalure type, comp. example 8, were investigated for their
structural composition.
[0257] The instrument used was a Zeiss 922 Omega (from Zeiss). It
was equipped with an Ultrascan 1000 CCD detector (from Gatan). The
imaging medium used was an electron beam, which illuminated the PVD
metallic effect pigments and their layer section uniformly and
largely in parallel. The acceleration voltage was 200 kV. The
electrons were scattered at inhomogeneities in the sample and
diffracted at lattice structures. After departing the layer, the
electrons were focused through an electron optical system into the
intermediate image plane, and, after passing through a further
magnification stage, were imaged by means of an electronic CCD
camera system. In this way, a real depiction of the illuminated
layer was obtained.
[0258] TEM micrographs of the inventive examples showed that metal
crystallites a few nanometers in size were present in a largely
amorphous matrix of metal oxide. FIG. 8a shows by way of example a
TEM micrograph for example 1.
[0259] In contrast, the comparative examples 8 and 9 showed a
fundamentally different structure to the materials described above.
The conventional metallic structure was found, with well-formed
crystals in different orientations. This is depicted by way of
example in FIG. 8b for comparative example 9.
[0260] The monoenergetic imaging electrons are diffracted at
crystalline structures as the beam passes through the samples. In
analogy to the Debye-Scherrer method in the case of fine crystal
powders in unordered orientations, the electron diffraction
reflections are located on circle arcs, at which the Bragg
conditions are met for the respective crystal network planes.
[0261] From the position, the distributions, and the intensities of
the diffraction reflections in the electron diffraction image it is
possible to show unambiguously that the diffracting structures of
the inventive examples consist of small crystallites of metallic
aluminum, chromium, or titanium. These crystallites are oriented
randomly and are in each case of a size and of a number such that
the respective reflections overlap to form a continuous diffraction
ring. This situation is shown by way of example in FIG. 9a for
inventive example 1. FIG. 10 shows by way of example the
measurement of the diffraction intensity for inventive example
1.
[0262] In contrast, comparative examples 8 and 9 have very sharply
defined and discrete diffraction reflections. This shows that only
a few large crystallites have participated in the diffraction. FIG.
9b shows these circumstances by way of example for comparative
example 9.
[0263] In the case of the inventive examples with aluminum metal
nanoparticles, moreover, a broad background of scattered
reflections is found. No reflections other than the Al diffraction
reflections are detectable, and hence it can be assumed that the
matrix surrounding the metal crystallites is amorphous.
[0264] The profile of the reflection intensity in the electron
diffraction image of the inventive chromium layers for example 2 or
3a shows that the diffraction maxima are located exactly in the
positions to be expected of metallic chromium, and show the
corresponding intensity distribution in the reciprocal space. The
reflections are significantly broadened, which likewise shows that
the diffracting metal crystals can only be of nanometer size. This
reliably verifies the existence of these Cr metal metal
nanoparticles. In addition to the chromium reflections, there is a
further reflection above a continuously descending intensity
background. This suggests that the chromium oxide is not
exclusively amorphous, but is instead in semicrystalline form.
[0265] Corresponding results are obtained for the titanium layer of
example 4b. Here again, very small metal crystallites are found in
a semicrystalline oxide matrix.
Part C: Characterization by Means of SEM and EDX Analytical Oxygen
Determination by Means of EDX Measurements:
[0266] The oxygen and metal composition of the layers in accordance
with inventive examples 1-7 and comparative examples 1-7 was
determined using the above-described measurement methodology by
means of EDX (instrument: EDAX Gemini; from EDAX Incorp., USA). A
match of the physical data was evident on the basis of the same
coating parameters, as already described above (under step 1).
Sample Preparation:
[0267] The layers were dispersed in a solvent and comminuted. A few
drops of the dispersion were applied to a sample plate, and the
solvent was slowly evaporated at room temperature. The layers took
on an orientation largely parallel to the plate surface.
Measurement:
[0268] The mean atomic ratio of oxygen to metal was determined for
the layers of the inventive examples.
[0269] For this purpose, first of all, a search was carried out,
using scanning electron micrographs, for regions in which at least
4 to 5 individual separate PVD layers were superimposed on one
another. Measurement was carried out at these locations. For the
measurements on the aluminum/aluminum oxide layers, an acceleration
voltage of 5 kV was selected; for the chromium/chromium oxide
layers, a voltage of 8 kV was operated. This ensured that, for
effective averaging, there were always two or more layers excited
simultaneously, without measurement of the substrate background as
well. Excitation took place in each case, for oxygen, of the K line
(excitation energy: about 0.5 keV), for chromium, of the K.alpha.
line (excitation energy: about 5.4 keV), and, for aluminum, of the
K.alpha. line (excitation energy; about 1.5 keV). The excited x-ray
spectrum was subjected to measurement, and the fraction of oxygen
and metal, respectively, was determined from the peak height ratio
with the aid of a software program.
TABLE-US-00002 TABLE 2 Physical data Layer Atomic Atomic
Nanoparticle Metallic or thickness oxygen oxygen fraction metal
nanoparticle Patent Vaporized from SEM [%] EDAX [%] ESCA from ESCA
fraction calculated Layer Substrate example substance [nm] analysis
analysis analysis via stoichiometry system Embossed 1 Al 33 44 27
One-layer 2 Cr 35-38 43-46 20 One-layer 3a Cr 23-25 53 12 3b Al
26-29 18 70 3c Cr 31-35 34 43 3 77 24 Three-layer 4a Al 24-26 see
FIG. 11a 4b Ti 80-87 see FIG. 11a 4 93-101 50-63 see Two-layer FIG.
11a 5 Al 30 30 One-layer 6 Al 112-119 54 10 One-layer 7a Al 53 38
37 7b Al 65 50 17 7c Al 49 48 20 7 Al 156-169 38 37 One-layer
Unembossed Comp. -1 Al 33 44 27 One-layer Comp. -2 Cr 35-38 43-46
20 One-layer Comp. -3a Cr 23-25 53 12 Comp. -3b Al 26-29 18 70
Comp. -3c Cr 31-35 34 43 Comp. -3 77 24 Three-layer Comp. -4a Al
24-26 see FIG. 12a Comp. -4b Ti 80-87 see FIG. 12a Comp. -4 93-101
50-63 see Two-layer FIG. 12a 5 Al 80 30 50 One-layer Comp. -6 Al
112-119 54 10 One-layer Comp. -7a Al 53 38 37 Comp. -7b Al 65 50 17
Comp. -7c Al 49 48 20 Comp. -7 Al 156-169 38 37 One-layer Comp. -8
Al 51-60 16 72 Comp. -9 Al 46-49 25 58 Comp. -9a Comp. -9b Comp.
-9c
Part D: Characterization of the Profile of Oxygen and Metal Over
the Layer Thickness from the Top Face a to the Bottom Face B for
Inventive Example 4 and Comparative Example 4 by Photoelectron
Spectroscopy (XPS/ESCA) and Sputter Profile Measurements.
[0270] For more precise structural characterization, the coated
films of inventive example 4 and of comparative example 4 were
analyzed by means of ESCA.
Analytical Methods and Instruments Used
Photoelectron Spectroscopy
[0271] Photoelectron spectroscopy (ESCA/XPS) can be used to provide
a quantitative determination of the atomic composition of the
surface of a sample. By means of high-resolution spectra, moreover,
it is possible to gain information concerning the chemical bonding
state of the individual elements. The information depth with this
method is approximately 5-10 nm, the detection limit approximately
0.1 to 1 atom %.
[0272] Measurement was carried out using an ESCALAB 250 instrument
from Thermo VG Scientific. Excitation took place using
monochromatic Al K.sub..alpha. x-ray radiation (15 kV, 150 W, 500
.mu.m spot size). The transmission function of the instrument was
measured on a copper sample. Charge compensation was done using a
"flood gun" with an electron energy of 6 eV/0.05 mA beam current.
The energy position was set for the evaluation such that the carbon
main line is at 285 eV.
[0273] The settings used for measuring the spectra were as
follows:
[0274] Overview spectra were measured with a pass energy of 80 eV,
high-resolution spectra with 30 eV. On nonmagnetic samples, the
magnet lens was used.
[0275] Quantitative figures for the surface composition were
calculated by means of Scofield factors on overview
measurements.
Sputter Depth Profile
[0276] For the individual samples, the below-listed distributions
of the elements in the depth are given by the depth profiles. The
profiles of the individual elements were prepared only to the
extent allowed by the data position in the spectra. When the
fraction of an element in the analyzed volume is very low, it is
not possible to make an unambiguous statement concerning the
oxidation state. The layer thickness is defined as the point at
which the fractions of the elements under consideration are of
equal size. In the case of different metals, the values of both
metals are always employed in this context.
Evaluation of Inventive Example 4 (see FIGS. 11a and 11b): [0277]
The titanium layer thickness is approximately 55 nm, the aluminum
layer thickness approximately 25 nm. [0278] Titanium at the surface
is predominantly in oxidized form. In the region from about 10-50
nm layer thickness, it is present in metallic form and in oxidized
form at equal fractions. [0279] Aluminum is less strongly oxidized
in the "middle" of the aluminum layer than at the layer margins. At
the film boundary, the degree of oxidation is higher than at the
titanium boundary. [0280] Carbon is present substantially as
substrate. Evaluation of Comparative Example 4 (see FIGS. 12a and
12b): [0281] The titanium layer thickness is approximately 75 nm,
the aluminum layer thickness approximately 25 nm. [0282] Titanium
at the surface is predominantly in oxidized form. In the region
from about 10-70 nm, it is present in metallic form and in oxidized
form at equal fractions. [0283] Aluminum is less strongly oxidized
in the "middle" of the aluminum layer than at the layer margins. At
the film boundary, the degree of oxidation is higher than at the
titanium boundary.
Part E: Colorimetric Evaluation of the Inventive Embossed PVD
Metallic Effect Pigments and of Pigment Types According to the
Prior Art
[0284] For colorimetric measurement (table 3) of the pigments of
inventive examples 1-6 and comparative examples 1-6 and also
comparative examples 8, 9, 9a, 9 and 9c, color cards were
produced.
TABLE-US-00003 TABLE 3 Substrate Patent example External appearance
of pigments Embossed 1 dark bluish metallic, prismatically lustrous
pigments 2 dark gray metallic, prismatically lustrous pigments 3a
3b 3c 3 dark gold, metallic, prismatically lustrous pigments 4a 4b
4 bluish silver metallic, prismatically lustrous pigments 5 gold,
metallically lustrous, prismatic pigments 6 dark gray metallic,
prismatically lustrous pigments 7a 7b 7c 7 dark gray metallic,
prismatically lustrous pigments Unembossed Comp.-1 dark bluish
metallically lustrous pigments Comp.-2 dark gray metallic,
prismatically lustrous pigments Comp.-3a Comp.-3b Comp.-3c Comp.-3
dark gold, metallically lustrous pigments Comp.-4a Comp.-4b Comp.-4
bluish silver metallic, prismatically lustrous pigments 5 gold,
metallically lustrous pigments Comp.-6 dark gray metallically
lustrous pigments Comp.-7a Comp.-7b Comp.-7c Comp.-7 dark gray
metallically lustrous pigments Embossed Comp.-8 silver metallic,
prismatically lustrous pigments Embossed Comp.-9 silver metallic,
prismatically lustrous pigments Embossed Comp.-9a brown prismatic
pigment mixture Embossed Comp.-9b brown prismatic pigment mixture
Embossed Comp.-9c brown-gray prismatic pigment mixture
[0285] For this purpose, geometrically equal coating areas as per
table 4 were detached from each of the carrier films and washed to
remove the release coat. Accordingly, except for examples 9b and
9c, the coating areas used were always the same.
[0286] The preliminary pigments of inventive examples 1-6 and
comparative examples 1-6 and 8 were thereafter suspended in 80 ml
of ethyl acetate and comminuted with a Turrax for 5 minutes at a
speed of rotation of 24 000 revolutions/min.
[0287] The resulting particle sizes (D50 values) are recorded here
in table 4.
[0288] The very coarse prismatic Metalure with a D50 of 50 .mu.m in
comparative example 9 and in comparative examples 9a, 9b, and 9c,
which was already present in pigment form, was comminuted
accordingly by the process as described above. For the blends of
comparative examples 9a, 9b, and 9c, comparative example 9 was
likewise comminuted and was thereafter available for the black
blends. The resulting particle size of comparative example 9 is
likewise recorded in table 4.
[0289] Each of the PVD metallic effect pigments from inventive
examples 1-6 and from comparative examples 1 and 6 and from
comparative examples 8 and 9 was incorporated by stirring as per
table 4 into the stated varnish system of a conventional
nitrocellulose varnish (Dr. Renger Erco Bronzemischlack 2615e; from
Morton). The pigments from comparative examples 9a, 9b, and 9c were
incorporated by stirring into a black varnish (5% Noir Covachip
W9702ET+20% butyl acetate+75% Intern. Lacquers Base 359). In view
of the smaller coating areas processed to pigments in comparative
examples 9b and 9c, different tints are obtained with the black
varnish. In each case, the PVD metallic effect pigment was
introduced and was then dispersed into the respective varnish
system with the aid of ethyl acetate.
[0290] The completed varnish was applied to #2853 test charts from
Byk Gardner (black-white contrast paper) in a wet film thickness of
12 .mu.m as specified in table 4, using a drawdown apparatus.
TABLE-US-00004 TABLE 4 Color preparations of fine pigments, applied
nonhidingly Detached Varnish system Knife pigment NC Black varnish
D50 depth Example area [m.sup.2] [g] [g] [.mu.m] [.mu.m] 1 0.435 2
10.75 12 2 0.435 2 8.11 12 3 0.435 2 17.85 12 4 0.435 2 30.14 12 5
0.435 2 17.5 12 6 0.435 2 20.8 12 Comp.-1 0.435 2 9.55 12 Comp.-2
0.435 2 9.25 12 Comp.-3 0.435 2 16.94 12 Comp.-4 0.435 2 20.5 12
Comp.-5 0.435 2 17.4 12 Comp.-6 0.435 2 20.5 12 Comp.-8 0.435 2
14.6 12 Comp.-9 0.435 2 -- 12.2 12 Comp.-9a 1 .times. 0.435 -- 2 12
Comp.-9b 1/4 .times. 0.435 -- 2 12 Comp.-9c 1/12 .times. 0.435 -- 2
12
[0291] With the levels of pigmentation of the inventive and
comparative examples, complete opacity was not practiced, and the
measurements were all carried out on the black contrast paper
coated with the knife drawdown.
[0292] Very thin wet film thicknesses have been found to be
particularly attractive, since they emphasize the prismatic effect
more strongly to a viewer than, for example, wet film thicknesses
of 24 .mu.m or around 50 .mu.m. Additionally it was found that with
the thin transparent inventive examples 1 and 2, a rainbow effect
can be obtained which has a blue-black shimmering edge.
Particularly effective here were, on the one hand, the metal
nanoparticles incorporated into the oxidic matrix, as strong
absorbers, and additionally, on the other hand, the black card
serves as a strong absorber. As a result of these effects of the
black card shimmering through and of the thin, wet film thickness,
therefore, it is possible to generate a high-grade color impression
of a rainbow with bluish black shimmering edging.
[0293] The subjective color impression was recorded by exemplary
illumination of the color cards in accordance with the schematic
illumination and observation arrangement as per FIG. 15, in table
5. For this purpose, an appropriate device was used to curve the
color cards produced, and the curved cards were illuminated by
means of three light sources in accordance with FIG. 15. In this
case the irradiated light on the one hand impinges vertically onto
the curved color card (middle lamp), and in the other case impinges
substantially at a 45.degree. angle onto the curved surface. The
viewer was then able to view the curved surface from different
angles and, accordingly, to simulate light conditions similar to
those for the colorimetric measurements (FIG. 16).
[0294] Table 5 summarizes the subjective color impressions of the
color cards (of the coated black card) illuminated in this way for
the three indicated reflection points 24, 25, and 26 as per FIG.
15.
TABLE-US-00005 TABLE 5 Color impression Color impression Color
impression as per area in regions of as per area illuminated at
vertical illuminated at approximately reflection approximately
45.degree. (left) (middle) 45.degree. (right) 1 strong prismatic
black lustrous strong prismatic blue-black blue-black shimmer
effect shimmer effect 2 strong prismatic black lustrous strong
prismatic blue-black blue-black shimmer effect shimmer effect 3
strong prismatic very intense strong prismatic effect gold lustrous
effect 4 strong prismatic blue silvery strong prismatic effect very
strongly effect lustrous 5 strong prismatic gold lustrous strong
prismatic effect effect 6 strong prismatic anthracite strong
prismatic effect lustrous effect Comp.-1 intense black black
lustrous intense black Comp.-2 intense black black lustrous intense
black Comp.-3 gold color very intense gold color flopping to dark
gold lustrous flopping to dark Comp.-4 blue silvery blue silvery
blue silvery shade flopping very strongly shade flopping to dark
lustrous to dark Comp.-5 gold color pale gold very gold color
flopping to dark strongly flopping to dark lustrous Comp.-6 shade
flopping anthracite shade flopping to dark lustrous to dark Comp.-8
strong prismatic silvery lustrous strong prismatic effect effect
Comp.-9 strong prismatic silvery lustrous strong prismatic effect
effect Comp.-9a prismatic with gray lustrous prismatic with
rustlike rustlike pixelation pixelation Comp.-9b prismatic with
dark gray prismatic with rustlike lustrous rustlike pixelation
pixelation Comp.-9c prismatic with very strongly prismatic with
rustlike dark gray rustlike pixelation lustrous pixelation
[0295] The knife drawdowns were subjected to colorimetry in
accordance with the manufacturer indications (Optronic Multiflash
instrument, Berlin, Germany). Irradiation took place at a constant
angle of 45.degree., and the CIELAB L*, a*, and b* values were
determined at observation angles of 15.degree., 20.degree.,
25.degree., 45.degree., 55.degree., 70.degree., 75.degree., and
110.degree. relative to the specular angle (illuminant: D65). This
arrangement is also shown exemplarily in FIG. 16.
[0296] In addition, the reflectivities of the knife drawdowns were
measured, in each case at the corresponding specular angles of
25.degree., 45.degree., and 75.degree., over the visible wavelength
range from 400-700 nm.
[0297] For investigation of the samples with regard to their
homogeneous appearance, the samples were additionally subjected to
measurement using a BYK-Mac colorimeter.
Colorimetric Assessment:
[0298] 1. Colorimetric Assessment of Black Blends of Comparative
Examples 9a, 9b, and 9c of Comparative Example 9 with Very Dark
Inventive Example 1
1.1 Assessment by Means of L*, H*, and C* Diagrams:
[0299] FIG. 13a here first shows the decrease in the lightnesses of
the L* values which are brought about by blending comparative
example 9 with a black varnish system, since within the black
varnish system the pigment fraction of comparative example 9 is
reduced in accordance with comparative examples 9a, 9b, and 9c. In
comparison to this, example 1 shows an even darker appearance even
at observation angles and specular angles of 45.degree..
[0300] The plotting of the H* values against the specular angle or
observation angle in accordance with FIG. 13b shows that the
prismatic effect in the case of inventive example 1 and of all the
comparative examples is clearly evident from the modulation of the
color locus in the 15-55.degree. range. Even in the case of
comparative example 9c, with its low concentration, the prismatic
effect is still developed. At high specular and observation angles
(70.degree.-110.degree., however, the comparative examples exhibit
a yellowish or brown color region. In contrast, inventive example 1
shows a distinct blue shade within this range.
[0301] The plotting of the C* values--FIG. 13c--for comparative
examples 9, 9a, 9b, and 9c shows the attenuation of the chroma
through the reduction in the prismatic pigment fraction of
comparative example 9 in the applications of the comparative
examples from 9a through 9b to 9c.
[0302] In comparison to the black varnish blends 9a, 9b, and 9c,
example 1 exhibits a surprisingly strong chroma at the observation
angles of 20.degree. and 25.degree.. Here, accordingly, the
prismatic effect is particularly strong. At 45.degree. and above,
the sample already appears to be only black-absorbing.
1.2 Assessment by the Plotting of the Spectra:
[0303] In order to reinforce and emphasize the colorimetric CIELAB
data, it is also possible to employ the recording of the spectra,
taken in the same operation, from FIG. 13d.
[0304] Interpretation of the spectra from 25.degree., 45.degree.
and 75.degree. over the visible wavelength range of 400-700 nm
shows, for comparative example 9, its characteristic profile, with
the strongest reflection in the blue region, with viewing direction
and direction of illumination as per FIG. 16 onto the color card
arranged at 45.degree..
[0305] In the case of comparative examples 9a, 9b, and 9c, the
reflectivity at an angle of 25.degree. is strongly reduced after
reduction of the pigment content in the blue wavelength range, and
a maximum reflectivity here is already observed at 45.degree.,
conversely, in the red wavelength range. At 75.degree. the
reflectivity relative to comparative example 9 is also reduced, but
not as greatly as in the case of inventive example 1.
[0306] Entirely surprisingly, the pigments of inventive example 1
in comparison show on the one hand a strong spectral splitting of
the light into the specular angle around 25.degree., with a maximum
in the blue wavelength range, and, on the other hand, a very strong
flop to dark at observation angles of just 45.degree. as per FIG.
15.
2. Colorimetric Assessment of Embossed Pigments Relative to
Pigments According to the Prior Art
[0307] In order to illustrate the difference between the embossed
pigments of inventive examples 1-6 and of comparative examples 8
and 9 relative to pigments without an embossed structure, it is
possible to employ the colorimetric evaluation of the H* profiles.
This comparison is made possible by FIGS. 14a and 14b.
[0308] Whereas, for all of the embossed examples, there is a
similar characteristic wavelike profile observable over the entire
color range ("rainbow"), comparative examples 1 and 4 exhibit a
horizontal profile. The gold-colored comparative examples 3 and 6,
in contrast, exhibit a steep flop of the gold color into the dark
region. None of the comparative examples gives a rainbow effect
even anywhere approximately close to that of the embossed
pigments.
3. Assessment for Homogeneity and of the "Sparkle Effect" of the
Color Cards:
[0309] The sparkle effect and the granular nature of a surface have
for a long time been available only to the subjective impression of
the viewer, and have not been quantifiable. In 2008, however, the
company BYK-Gardner brought onto the market a new instrument
(BYK-mac.RTM.) allowing these effects to be quantified for the
first time. The sparkle effect is generated with the aid of very
bright white LED lamps which illuminate the surface from three
different illumination angles (15.degree., 45.degree., and
75.degree. relative to the normal). The granularity is visualized
by diffuse illumination of the surface with the aid of an Ulbricht
sphere. Using a high-resolution CCD camera placed perpendicular to
the surface, an image is taken of the surface, and an
instrument-internal algorithm calculates for each illumination
direction, from the intensity and distribution of the lightness
patterns, the "sparkle intensity", which reflects the lightness of
the individual faces; the "sparkle area", as a measure of the total
surface area of the sparkling points; and also the granularity
characteristic. Derived from the two sparkle parameters is the
"degree of sparkle", which correlates to the visual impression: the
higher this figure, the greater the extent to which an observer
perceives the sparkle effect of a surface.
[0310] The abovementioned drawdowns of the inventive examples and
of the comparative examples in accordance with table 4 were
subjected to measurement accordingly using this instrument.
[0311] The results of the measurements showed that a more
homogeneous appearance was produced with the embossed structure
selected--FIG. 18--of the inventive examples, in comparison to
comparative example 9, with an embossed structure in the form of a
linear pattern.
* * * * *